Resist composition and patterning process

ABSTRACT

To a resist composition comprising a polymer which changes its alkali solubility under the action of an acid as a base resin, is added a copolymer comprising recurring units containing amino and recurring units containing α-trifluoromethylhydroxy as an additive. The composition is suited for immersion lithography.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 2007-176011 filed in Japan on Jul. 4, 2007,the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to resist compositions for use in the lithographytechnology for the microfabrication of semiconductor devices or thelike, especially the immersion photolithography utilizing an ArF excimerlaser of wavelength 193 nm as the light source and interposing waterbetween a projection lens and a wafer. It also relates to a patterningprocess using the resist compositions.

BACKGROUND ART

In the recent drive for higher integration and operating speeds in LSIdevices, the pattern rule is made drastically finer. Thephotolithography which is currently on widespread use in the art isapproaching the essential limit of resolution determined by thewavelength of a light source.

As the light source used in the lithography for resist patternformation, g-line (436 nm) or i-line (365 nm) from a mercury lamp waswidely used. One means believed effective for further reducing thefeature size is to reduce the wavelength of exposure light. For the massproduction process of 64 MB dynamic random access memories (DRAM,processing feature size 0.25 μm or less) and later ones, the exposurelight source of i-line (365 nm) was replaced by a KrF excimer laserhaving a shorter wavelength of 248 nm.

However, for the fabrication of DRAM with a degree of integration of 256MB and 1 GB or more requiring a finer patterning technology (processingfeature size 0.2 μm or less), a shorter wavelength light source isrequired. Over a decade, photolithography using ArF excimer laser light(193 nm) has been under active investigation.

It was expected at the initial that the ArF lithography would be appliedto the fabrication of 180-nm node devices. However, the KrF excimerlithography survived to the mass-scale fabrication of 130-nm nodedevices. So, the full application of ArF lithography started from the90-nm node. The ArF lithography combined with a lens having an increasednumerical aperture (NA) of 0.9 is considered to comply with 65-nm nodedevices.

For the next 45-nm node devices which required an advancement to reducethe wavelength of exposure light, the F₂ lithography of 157 nmwavelength became a candidate. However, for the reasons that theprojection lens uses a large amount of expensive CaF₂ single crystal,the scanner thus becomes expensive, hard pellicles are introduced due tothe extremely low durability of soft pellicles, the optical system mustbe accordingly altered, and the etch resistance of resist is low; thepostponement of F₂ lithography and the early introduction of ArFimmersion lithoqraphy were advocated (see Proc. SPIE Vol. 4690 xxix).

In the ArF immersion lithography, the space between the projection lensand the wafer is filled with water. Since water has a refractive indexof 1.44 at 193 nm, pattern formation is possible even using a lens withNA of 1.0 or greater. Theoretically, it is possible to increase the NAto 1.35. The resolution is improved by an increment of NA. A combinationof a lens having NA of at least 1.2 with ultra-high resolutiontechnology suggests a way to the 45-nm node (see Proc. SPIE Vol. 5040,p724).

However, for resist materials, as the circuit line width is reduced, theinfluence of acid diffusion on contrast becomes more serious. This isbecause the pattern size is approaching the diffusion length of acid,and leads to a lowering of mask fidelity and a degradation of patternrectangularity. Therefore, in order to take full advantage of thereduced wavelength of a light source and the increased NA, it isnecessary to increase the dissolution contrast over prior art materialsand to restrain the acid diffusion.

With respect to the immersion lithography, several problems associatedwith the presence of water on resist were pointed out. Because thephotoacid generator in the resist film, the acid generated therefromupon exposure, and the amine compound added to the resist as a quenchercan be leached in water in contact with the resist film, pattern profilechanges occur. The pattern collapses due to swelling of the resist filmwith water.

With respect to the leaching of resist components into water, a studystarted from the standpoint of preventing the projection lens of thelithography system from contamination. Several lithography systemmanufacturers proposed the limit of leach-outs.

For overcoming these problems, it was proposed to provide a protectivecoating of perfluoroalkyl compound between the resist film and water(see the 2nd Immersion Workshop, Jul. 11, 2003, Resist and CoverMaterial Investigation for Immersion Lithography). The provision of sucha protective coating avoids direct contact between the resist film andwater and inhibits the resist film from being leached with water.

However, protective coatings made of perfluoroalkyl compounds usefluorocarbons like Freon® as the diluent for controlling a coatingthickness. As is well known, the use of fluorocarbons is a considerationin view of environmental protection. In addition, the protective coatingmust be stripped using fluorocarbon, prior to development of the resistfilm. Therefore, special units for coating and stripping of theprotective film must be added to the existing system. Fluorocarbonsolvents add to the expense. These factors raise serious problems onpractical use.

One means proposed for mitigating practical drawbacks of the protectivefilm of solvent stripping type is a protective film of the type which issoluble in alkaline developer (JP-A 2005-264131). The alkali-solubleprotective film is epoch-making in that it eliminates a need for astripping step or a special stripping unit because it can be strippedoff at the same time as the development of a photoresist film.

The ArF immersion lithography systems commercially lo available at thepresent are designed such that water is partly held between theprojection lens and the wafer rather than immersing the resist-coatedsubstrate fully in water, and exposure is carried out by scanning thewafer-holding stage at a speed of 300 to 550 mm/sec. Because of suchhigh-speed scanning, water cannot be held between the projection lensand the wafer, and water droplets are left on the surface of the resistfilm or protective film after scanning. It is believed that residualdroplets cause defective pattern formation.

To eliminate the droplets remaining on the surface of the photoresist orprotective film after scanning, it is necessary to improve the flow ormobility of water on the relevant coating film. It is reported that thenumber of defects associated with the immersion lithography can bereduced by increasing the receding contact angle of the photoresist orprotective film with water. See 2nd International Symposium on ImmersionLithography, 12-15 Sept., 2005, Defectivity data taken with a full-fieldimmersion exposure tool, Nakano et al. It is noted that the method ofmeasuring a receding contact angle includes a sliding method ofinclining a substrate and a suction method of sucking up water, with thesliding method being widely accepted.

If residues are left on the resist film after development, there arisedefects which are known as blobs. The blob defects occur because theprotective coating or resist material is precipitated during rinsingafter development and deposited on the resist film again, and are foundmore often when the resist film after development is more hydrophobic.For the resist for use in the immersion lithography in combination witha protective coating, if mixing occurs between the protective coatingand the resist coating, the hydrophobic protective coating can be lefton the surface of the resist coating after development, leading to blobdefects on the resist coating. It is then necessary to preventintermixing between the protective coating and the resist coating sothat no protective coating is left after development.

DISCLOSURE OF THE INVENTION

An object of the invention is to provide a photoresist composition whichwhen coated as photoresists, forms a resist layer having a surfacemodified so as to improve dissolution contrast for thereby improvingpattern rectangularity and mask fidelity, wherein in the immersionlithography, the resist layer prevents intermixing between resist andprotective layers when a protective layer is formed on the resist layer,and the resist layer on its surface is more hydrophilic after exposureand development, thus preventing blob defects from generating.

Another object is to provide a patterning process using the resistcomposition.

In a first aspect, the invention provides a resist compositioncomprising a polymer which changes its alkali solubility under theaction of an acid as a base resin, and a copolymer comprising recurringunits containing an amino group and recurring units containing at leastone fluorine atom as an additive.

In a preferred embodiment, the copolymer has the general formula (1) or(2).

Herein R¹, R⁴, and R⁷ are each independently hydrogen or methyl. X₁ andY2 are each independently a single bond, —O—R⁹—, —C(═O)—O—R⁹—,—C(═O)—NH—R⁹—, a straight or branched C₁-C₄ alkylene, or phenylenegroup, wherein R⁹ is a straight, branched or cyclic C₁-C₁₀ alkylenegroup which may contain an ester or ether group. The subscript n is 1 or2. In case of n=1, Y₁ is a single bond, —O—R⁹—, —C(—O)—O—R⁹—,—C(═O)—NH—R⁹—, a straight or branched C₁-C₄ alkylene, or phenylenegroup, wherein R⁹ is as defined above. In case of n=2, Y₁ is —O—R¹⁰¹═,—C(═O)—O—R¹⁰¹═, —C(═O)—NH—R¹⁰¹═, a straight or branched C₁-C₄ alkylenegroup with one hydrogen atom eliminated, or a phenylene group with onehydrogen atom eliminated, wherein R¹⁰¹ is a straight, branched or cyclicC₁-C₁₀ alkylene group with one hydrogen atom eliminated which maycontain an ester or ether group. R² and R³ are each independentlyhydrogen, a straight, branched or cyclic C₁-C₂₀ alkyl group, a C₂-C₂₀alkenyl group, or a C₆-C₁₀ aryl group, or R² and R³ may bond together toform a ring of 3 to 20 carbon atoms with the nitrogen atom to which theyare attached, the alkyl group, alkenyl group, aryl group or the ring maycontain a hydroxy, ether, ester, cyano, amino group, double bond orhalogen atom, or R² and X₁ may bond together to form a ring of 3 to 20carbon atoms with the nitrogen atom to which they are attached, R⁵ is astraight, branched or cyclic C₁-C₁₂ alkylene group, R⁶ is hydrogen,fluorine, methyl, trifluoromethyl or difluoromethyl, or R⁵ and R⁶ maybond together to form an aliphatic ring of 2 to 12 carbon atoms with thecarbon atom to which they are attached, which ring may contain an ethergroup, fluorinated alkylene group or trifluoromethyl group. R⁸ is astraight, branched or cyclic C₁-C₂₀ alkyl group which has at least onefluorine atom substituted thereon and which may contain an ether, esteror sulfonamide group. The subscripts are numbers in the range: 0<a<1.0,0≦(b-1)<1.0, 0≦(b-2)<1.0, 0<(b-1)+(b-2)<1.0, and 0.5≦a+(b-1)+(b-2) ≦1.0.

Herein R¹, R⁴, R⁷, and R¹⁰ are each independently hydrogen or methyl. X₁and Y2 are each independently a single bond, —O—R⁹—, —C(═O)—O—R⁹—,—C(═O)—NH—R⁹—, a straight or branched C₁-C₄ alkylene, or phenylenegroup, wherein R⁹ is a straight, branched or cyclic C₁-C₁₀ alkylenegroup which may contain an ester or ether group. The subscripts n and mare each independently 1 or 2. In case of n=1 and m=1, Y₁ and Y₃ areeach independently a single bond, —O—R⁹—, —C(═O)—O—R⁹—, —C(═O)—NH—R⁹—, astraight or branched C₁-C₄ alkylene, or phenylene group, wherein R⁹ isas defined above. In case of n=2 and m=2, Y₁ and Y₃ are eachindependently —O—R¹⁰¹═, —C(═O)—O—R¹⁰¹═, —C(═O)—NH—R¹⁰¹═l, a straight orbranched C₁-C₄ alkylene group with one hydrogen atom eliminated, or aphenylene group with one hydrogen atom eliminated, wherein R¹⁰¹ is astraight, branched or cyclic C₁-C₁₀ alkylene group with one hydrogenatom eliminated which may contain an ester or ether group. R² and R³ areeach independently hydrogen, a straight, branched or cyclic C₁-C₂₀ alkylgroup, a C₂-C₂₀ alkenyl group, or a C₆-C₁₀ aryl group, R² and R³ maybond together to form a ring of 3 to 20 carbon atoms with the nitrogenatom to which they are attached, the alkyl group, alkenyl group, arylgroup or the ring may contain a hydroxy, ether, ester, cyano, aminogroup, double bond or halogen atom, or R² and X₁ may bond together toform a ring of 3 to 20 carbon atoms with the nitrogen atom to which theyare attached, R⁵ and R¹¹ are each independently a straight, branched orcyclic C₁-C₁₂ alkylene group, R⁶ and R¹² are each independentlyhydrogen, fluorine, methyl, trifluoromethyl or difluoromethyl.Alternatively, R⁵ and R⁶ may bond together to form an aliphatic ring of2 to 12 carbon atoms with the carbon atom to which they are attached,which ring may contain an ether group, fluorinated alkylene group ortrifluoromethyl group, and R¹¹ and R¹² may bond together to form analiphatic ring of 2 to 12 carbon atoms with the carbon atom to whichthey are attached, which ring may contain an ether group, fluorinatedalkylene group or trifluoromethyl group. R⁸ is a straight, branched orcyclic C₁-C₂₀ alkyl group which has at least one fluorine atomsubstituted thereon and which may contain an ether, ester or sulfonamidegroup. R¹³ is an acid labile group. The subscripts are numbers in therange: 0<a<1.0, 0≦(b-1)<1.0, 0≦(b-2)<1.0, 0<(b-3)<1.0, and0.5≦a+(b-1)+(b-2)+(b-3)≦1.0.

Typically the resist composition is a chemically amplified resistcomposition which may be either positive or negative. When the resistcomposition is positive, the base resin is specifically a polymercomprising recurring units having acid labile groups and recurring unitshaving hydroxy groups and/or adhesive groups of lactone ring.

Where the base resin includes recurring units having hydroxy groupsand/or adhesive groups of lactone ring, the chemically amplifiedpositive resist composition ensures tight adhesion to a substrate. Wherethe base resin includes recurring units having acid labile groups, theacid labile groups are deprotected with the acid generated by the acidgenerator during exposure so that the exposed area of resist isconverted to be soluble in a developer, ensuring that a pattern isformed at a very high precision.

Also preferably the resist composition further comprises at least onemember selected from among an organic solvent, a basic compound, adissolution regulator, a crosslinker, and a surfactant.

The inclusion of an organic solvent can facilitate to coat the resistcomposition to substrates or the like. The inclusion of a basic compoundcan hold down the diffusion rate of acid within the resist film, leadingto a further improved resolution. The inclusion of a dissolutionregulator can increase the difference in dissolution rate betweenexposed and unexposed areas, leading to a further improved resolution.The addition of a surfactant can further facilitate or control thecoating operation of the resist composition. For the chemicallyamplified resist composition which is negative, a crosslinker iscompounded.

In another aspect, the invention provides a pattern forming processcomprising the steps of applying the aforementioned resist compositiononto a substrate to form a coating, heat treating the coating andexposing it to high-energy radiation, and developing the exposed coatingwith a developer. The step of heat treatment may be included after theexposing step and before the developing step. The process may furtherinclude subsequent steps such as etching, resist removal and cleaning.Preferably the high-energy radiation has a wavelength of 180 to 250 nm.

In preferred embodiments, the exposing step is by immersion lithographyinvolving exposing the coating to high-energy radiation through aliquid. The process may further comprise the step of forming aprotective coating so that the protective coating intervenes between thephotoresist coating and the liquid during the immersion lithography. Theprotective coating is typically an alkali-soluble protective film basedon a polymer having α-trifluoromethylhydroxy groups.

The immersion lithography may involve using high-energy radiation havinga wavelength of 180 to 250 nm, introducing a liquid between thesubstrate which has been coated with resist and protective films and aprojection lens, and exposing the substrate to the high-energy radiationthrough the liquid. The liquid is typically water.

BENEFITS OF THE INVENTION

The inventive resist composition has the advantages of patternrectangularity and mask fidelity. The photoresist film formed from thecomposition has a surface which is hydrophilic enough to prevent blobdefects from generating on the resist film after development. The resistfilm also prevents intermixing between the resist film and a protectivelayer which is formed in the immersion lithography for protecting theresist film, thus preventing the pattern profile from being degraded.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The terms “a” and “an” herein do not denote a limitation of quantity,but rather denote the presence of at least one of the referenced item.

As used herein, the notation (C_(n)-C_(m)) means a group containing fromn to m carbon atoms per group.

The abbreviation “phr” refers to parts by weight per 100 parts by weightof resin.

The inventors have found that (1) a photoresist composition comprising aspecific polymer additive compounded therein exhibits a very highresolution and is improved especially in pattern rectangularity and maskfidelity. In the immersion lithography, a protective layer is formed ona photoresist layer, and water is held between the protective layer anda projection lens. We have also found that (2) a photoresist layerformed from the composition is effective for preventing intermixingbetween the resist layer and the protective layer; and (3) thephotoresist layer presents a surface which is more hydrophilic afterdevelopment, for preventing defect generation. Further studying thecomposition and compounding of the polymer additive, we have completedthe invention.

Polymeric Surfactant

The resist composition of the invention is defined as comprising (A) apolymer which changes its alkali solubility under the action of an acidas a base resin, and (B) a copolymer comprising recurring unitscontaining an amino group and recurring units containing at least onefluorine atom as an additive.

In a preferred embodiment of the polymer (B) as polymeric additive, therecurring units containing an amino group and recurring units containingat least one fluorine atom are represented by the general formula (1) or(2).

Herein R¹, R⁴, and R⁷ are each independently hydrogen or methyl. X₁ andY2 are each independently a single bond, —O—R⁹—, —C(═O)—O—R⁹—,—C(═O)—NH—R⁹—, a straight or branched C₁-C₄ alkylene group, or aphenylene group, wherein R⁹ is a straight, branched or cyclic C₁-C₁₀alkylene group which may contain an ester (—COO—) or ether (—O—) group.The subscript n is 1 or 2. In case of n=1, Y₁ is a single bond, —O—R⁹—,—C(═O)—O—R⁹—, —C(═O)—NH—R⁹—, a straight or branched C₁-C₄ alkylenegroup, or a phenylene group, wherein R⁹ is as defined above. In case ofn=2, Y₁ is —O—R¹⁰¹═, —C(═O)—O—R¹⁰¹═, —C(═O)—NH—R¹⁰¹═, a straight orbranched C₁-C₄ alkylene group with one hydrogen atom eliminated, or aphenylene group with one hydrogen atom eliminated, wherein R¹⁰¹ is astraight, branched or cyclic C₁-C₁₀ alkylene group with one hydrogenatom eliminated which may contain an ester or ether group. R² and R³ areeach independently hydrogen, a straight, branched or cyclic C₁-C₂₀ alkylgroup, a C₂-C₂₀ alkenyl group, or a C₆-C₁₀ aryl group, or R² and R³ maybond together to form a ring of 3 to 20 carbon atoms with the nitrogenatom to which they are attached, the alkyl group, alkenyl group, arylgroup or the ring may contain a hydroxy, ether, ester, cyano, aminogroup, double bond or halogen atom, or R² and X₁ may bond together toform a ring of 3 to 20 carbon atoms with the nitrogen atom to which theyare attached, R⁵ is a straight, branched or cyclic C₁-C₁₂ alkylenegroup, R⁶ is hydrogen, fluorine, methyl, trifluoromethyl ordifluoromethyl, or R⁵ and R⁶ may bond together to form an aliphatic ringof 2 to 12 carbon atoms, especially 3 to 10 carbon atoms, with thecarbon atom to which they are attached, which ring may contain an ethergroup, fluorinated alkylene group or trifluoromethyl group. R⁸ is astraight, branched or cyclic C₁-C₂₀ alkyl group which has at least onefluorine atom substituted thereon and which may contain an ether, esteror sulfonamide group. The subscripts are numbers in the range: 0<a<1.0,0≦(b-1)<1.0, 0≦(b-2)<1.0, 0<(b-1)+(b-2)<1.0, and 0.5≦a+(b-1)+(b-2)≦1.0.

Herein R¹, R⁴, R⁷, and R¹⁰ are each independently hydrogen or methyl. X₁and Y2 are each independently a single bond, —O—R⁹—, —C(═O)—O—R⁹—,—C(═O)—NH—R⁹—, a straight or branched C₁-C₄ alkylene group, or aphenylene group, wherein R⁹ is a straight, branched or cyclic C₁-C₁₀alkylene group which may contain an ester or ether group. The subscriptsn and m are each independently 1 or 2. In case of n=1 and m=1, Y₁ and Y₃are each independently a single bond, —O—R⁹—, —C(═O)—O—R⁹—,—C(═O)—NH—R⁹—, a straight or branched C₁-C₄ alkylene group, or aphenylene group, wherein R⁹ is as defined above. In case of n=2 and m=2,Y₁ and Y₃ are each independently —O—R¹⁰¹═, —C(═O)—O—R¹⁰¹═,—C(═O)—NH—R¹⁰¹═a straight or branched C₁-C₄ alkylene group with onehydrogen atom eliminated, or a phenylene group with one hydrogen atomeliminated, wherein R¹⁰¹ is a straight, branched or cyclic C₁-C₁₀alkylene group with one hydrogen atom eliminated which may contain anester or ether group. R² and R³ are each independently hydrogen, astraight, branched or cyclic C₁-C₂₀ alkyl group, a C₁-C₂₀ alkenyl group,or a C₆-C₁₀ aryl group. Alternatively, R² and R³ may bond together toform a ring of 3 to 20 carbon atoms with the nitrogen atom to which theyare attached, the alkyl group, alkenyl group, aryl group or the ring maycontain a hydroxy, ether, ester, cyano, amino group, double bond orhalogen atom, or R² and X₁ may bond together to form a ring of 3 to 20carbon atoms with the nitrogen atom to which they are attached, R⁵ andR¹¹ are each independently a straight, branched or cyclic C₁-C₁₂alkylene group, R⁶ and R¹² are each independently hydrogen, fluorine,methyl, trifluoromethyl or difluoromethyl. Alternatively, R⁵ and R⁶ maybond together to form an aliphatic ring of 2 to 12 carbon atoms with thecarbon atom to which they are attached, and R¹¹ and R¹² may bondtogether to form an aliphatic ring of 2 to 12 carbon atoms with thecarbon atom to which they are attached, while the alicyclic may containan ether group, fluorinated alkylene group or trifluoromethyl group. R⁸is a straight, branched or cyclic C₁-C₂₀ alkyl group which has at leastone fluorine atom substituted thereon and which may contain an ether,ester or sulfonamide group. R¹³ is an acid labile group. The subscriptsare numbers in the range: 0<a<1.0, 0≦(b-1)<1.0, 0≦(b-2)<1.0,0<(b-3)<1.0, and 0.5≦a+(b-1)+(b-2)+(b-3)≦1.0.

The photoresist composition of the invention is characterized by theaddition of a surfactant in polymeric form having an amino group and afluoroalkyl group, as represented by formula (1) or (2). The amino groupfunctions as a quencher to the acid generated upon exposure. While theconcentration distribution of acid generated is such that a layer closerto the surface has a higher acid concentration, and shows morenoticeable changes under lower optical contrast conditions, the additionof the polymeric surfactant of formula (1) or (2) prevents theconcentration of acid generated in the surface layer from becomingexcessive and thus improves dissolution contrast, thereby forming apattern in a rectangular profile and improving mask fidelity. In thecase of a hole pattern, side lobe resistance is improved. When aphotoresist layer is formed, the amino groups are oriented on the resistlayer surface, whereby the resist layer surface becomes hydrophilic,restraining occurrence of blob defects following development. In oneexemplary immersion lithography, following formation of a photoresistlayer, a protective coating is applied thereon as a topcoat. Theprotective coating is preferably formed of such a material that meetsboth alkali solubility and water repellency, specifically a materialcomprising a polymer having α-trifluoromethylhydroxy groups as a base ina solvent in which the resist layer is not dissolved and which isselected from higher alcohols of 4 or more carbon atoms, ethers,alkanes, fluorinated solvents in which one or more hydrogen atoms of thehigher alcohol, ether or alkane are substituted by fluorine atom, andthe like. Since the polymeric surfactant having amino groups andfluoroalkyl groups according to the invention is not soluble at all inthe solvent for the protective coating material, it provides a barrierlayer for preventing intermixing between the protective layer and theresist layer. Thus, the profile of a resist pattern after developmentremains unchanged whether or not a protective layer is used. A resistpattern of good profile is always obtainable.

Examples of suitable polymerizable monomers from which recurring units“a” in formulae (1) and (2) are derived are given below.

Herein R¹ is as defined above

Examples of suitable monomers from which recurring units (b-1) having anα-trifluoromethylalcohol group in formulae (1) and (2) are derived aregiven below.

Herein R⁴ is as defined above.

Examples of the monomers from which recurring units (b-2) in formulae(1) and (2) are derived are given below.

Herein R⁷ is as defined above.

The monomers from which recurring units (b-3) in formula (2) are derivedinclude the exemplary compounds, shown below, having the structurewherein the trifluoromethyl alcohol represented by recurring units (b-1)in formulae (1) and (2) is protected with an acid labile group R¹³,which will be described later.

Herein R¹⁰ is as defined above.

The acid labile groups represented by R¹³ may be selected from a varietyof such groups. Examples of the acid labile group are groups of thefollowing general formulae (L1) to (L4), tertiary alkyl groups of 4 to20 carbon atoms, preferably 4 to 15 carbon atoms, trialkylsilyl groupsin which each alkyl moiety has 1 to 6 carbon atoms, and oxoalkyl groupsof 4 to 20 carbon atoms.

The broken line indicates a valence bond.

In formula (L1), R^(L01) and R^(L02) are hydrogen or straight, branchedor cyclic alkyl groups of 1 to 18 carbon atoms, preferably 1 to 10carbon atoms. Examples include hydrogen, methyl, ethyl, propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, cyclopentyl, cyclohexyl,2-ethylhexyl, n-octyl, and adamantyl. R^(L03) is a monovalenthydrocarbon group of 1 to 18 carbon atoms, preferably 1 to 10 carbonatoms, which may contain a hetero atom such as oxygen, examples of whichinclude unsubstituted straight, branched or cyclic alkyl groups andstraight, branched or cyclic alkyl groups in which some hydrogen atomsare replaced by hydroxyl, alkoxy, oxo, amino, alkylamino or the like.Examples of the straight, branched or cyclic alkyl groups are asexemplified above for R^(L01) and R^(L02), and examples of thesubstituted alkyl groups are shown below.

A pair of R^(L01) and R^(L02), R^(L01) and R^(L03), or R^(L02) andR^(L03) may bond together to form a ring with the carbon and oxygenatoms to which they are attached. Each of R^(L01), R^(L02) and R^(L03)is a straight or branched alkylene group of 1 to 18 carbon atoms,preferably 1 to 10 carbon atoms when they form a ring.

In formula (L2), R^(L04) is a tertiary alkyl group of 4 to 20 carbonatoms, preferably 4 to 15 carbon atoms, a trialkylsilyl group in whicheach alkyl moiety has 1 to 6 carbon atoms, an oxoalkyl group of 4 to 20carbon atoms, or a group of formula (L1). Exemplary tertiary alkylgroups are tert-butyl, tert-amyl, 1,1-diethylpropyl,2-cyclopentylpropan-2-yl, 2-cyclohexylpropan-2-yl,2-(bicyclo[2.2.1]heptan-2-yl)propan-2-yl, 2-(adamantan-1-yl)propan-2-yl,1-ethylcyclopentyl, 1-butylcyclopentyl, 1-ethylcyclohexyl,1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl, 1-ethyl-2-cyclohexenyl,2-methyl-2-adamantyl, and 2-ethyl-2-adamantyl. Exemplary trialkylsilylgroups are trimethylsilyl, triethylsilyl, and dimethyl-tert-butylsilyl.Exemplary oxoalkyl groups are 3-oxocyclohexyl, 4-methyl-2-oxooxan-4-yl,and 5-methyl-2-oxooxolan-5-yl. In formula (L2), y is an integer of 0 to6.

In formula (L3), R^(L05) is a substituted or unsubstituted, straight,branched or cyclic C₁-C₁₀ alkyl group or a substituted or unsubstitutedC₆-C₂₀ aryl group. Examples of the substituted or unsubstituted alkylgroups include straight, branched or cyclic ones such as methyl, ethyl,propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl,n-hexyl, cyclopentyl, cyclohexyl and bicyclo[2.2.1]heptyl; substitutedforms of the foregoing in which some hydrogen atoms are replaced byhydroxyl, alkoxy, carboxy, alkoxycarbonyl, oxo, amino, alkylamino,cyano, mercapto, alkylthio, sulfo or other groups; and substituted formsof the foregoing in which some of the methylene groups are replaced byoxygen or sulfur atoms. Exemplary substituted or unsubstituted arylgroups are phenyl, methylphenyl, naphthyl, anthryl, phenanthryl, andpyrenyl. In formula (L3), m is 0 or 1, n is 0, 1, 2 or 3, and 2m+n isequal to 2 or 3.

In formula (L4), R^(L06) is a substituted or unsubstituted, straight,branched or cyclic C₁-C₁₀ alkyl group or a substituted or unsubstitutedC₆-C₂₀ aryl group. Examples of these groups are the same as exemplifiedfor R^(L05). R^(L07) to R^(L16) independently represent hydrogen ormonovalent C₁-C₁₅ hydrocarbon groups. Exemplary hydrocarbon groups arestraight, branched or cyclic alkyl groups such as methyl, ethyl, propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl,n-octyl, n-nonyl, n-decyl, cyclopentyl, cyclohexyl, cyclopentylmethyl,cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyland cyclohexylbutyl, and substituted forms of the foregoing in whichsome hydrogen atoms are replaced by hydroxyl, alkoxy, carboxy,alkoxycarbonyl, oxo, amino, alkylamino, cyano, mercapto, alkylthio,sulfo or other groups. Alternatively, two of R^(L07) to R^(L03) may bondtogether to form a ring with the carbon atom to which they are attached(for example, a pair of R^(L07) and R^(L08), R^(L07) and R^(L09),R^(L08) and R^(L10), R^(L09) and R^(L10), R^(L11) and R^(L12), R^(L13)and R^(L14), or a similar pair form a ring). Each of R^(L07) to R^(L16)represents a divalent C₁-C₁₅ hydrocarbon group when they form a ring,examples of which are the ones exemplified above for the monovalenthydrocarbon groups, with one hydrogen atom being eliminated. Two ofR^(L07) to R^(L16) which are attached to vicinal carbon atoms (forexample, a pair of R^(L07) and R^(L09), R^(L09) and R^(L15), R^(L13) andR^(L15), or a similar pair) may bond together directly to form a doublebond.

Of the acid labile groups of formula (L1), the straight and branchedones are exemplified by the following groups.

Of the acid labile groups of formula (L1), the cyclic ones are, forexample, tetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl,tetrahydropyran-2-yl, and 2-methyltetrahydropyran-2-yl.

Examples of the acid labile groups of formula (L2) includetert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-amyloxycarbonyl,tert-amyloxycarbonylmethyl, 1,1-diethylpropyloxycarbonyl,1,1-diethylpropyloxycarbonylmethyl, 1-ethylcyclopentyloxycarbonyl,1-ethylcyclopentyloxycarbonylmethyl, 1-ethyl-2-cyclopentanyloxycarbonyl,1-ethyl-2-cyclopentenyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl,2-tetrahydropyranyloxycarbonylmethyl, and2-tetrahydrofuranyloxycarbonylmethyl groups.

Examples of the acid labile groups of formula (L3) include1-methylcyclopentyl, 1-ethylcyclopentyl, 1-n-propylcyclopentyl,1-isopropylcyclopentyl, 1-n-butylcyclopentyl, 1-sec-butylcyclopentyl,1-cyclohexylcyclopentyl, 1-(4-methoxy-n-butyl)cyclopentyl,1-(bicyclo[2.2.1]heptan-2-yl)cyclopentyl,1-(7-oxabicyclo[2.2.1]heptan-2-yl)cyclopentyl, 1-methylcyclohexyl,1-ethylcyclohexyl, 3-methyl-1-cyclopenten-3-yl,3-ethyl-1-cyclopenten-3-yl, 3-methyl-1-cyclohexen-3-yl, and3-ethyl-1-cyclohexen-3-yl groups.

The acid labile groups of formula (L4) are preferably groups of thefollowing formulae (L4-1) to (L4-4).

In formulae (L4-1) to (L4-4), the broken line indicates a bonding siteand direction. R^(L41) is each independently selected from monovalenthydrocarbon groups, typically straight, branched or cyclic C₁-C₁₀ alkylgroups, for example, methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl, andcyclohexyl.

For formulas (L4-1) to (L4-4), there can exist enantiomers anddiastereomers. Each of formulae (L4-1) to (L4-4) collectively representsall such stereoisomers. Such stereoisomers may be used alone or inadmixture.

For example, the general formula (L4-3) represents one or a mixture oftwo selected from groups having the following general formulas (L4-3-1)and (L4-3-2).

Herein R^(L41) is as defined above.

Similarly, the general formula (L4-4) represents one or a mixture of twoor more selected from groups having the following general formulas(L4-4-1) to (L4-4-4).

Herein R^(L41) is as defined above.

Each of formulas (L4-1) to (L4-4), (L4-3-1) and (L4-3-2), and (L4-4-1)to (L4-4-4) collectively represents an enantiomer thereof and a mixtureof enantiomers.

It is noted that in the above formulas (L4-1) to (L4-4), (L4-3-1) and(L4-3-2), and (L4-4-1) to (L4-4-4), the bond direction is on the exoside relative to the bicyclo[2.2.1]heptane ring, which ensures highreactivity for acid catalyzed elimination reaction (see JP-A2000-336121). In preparing these monomers having a tertiary exo-alkylgroup of [2.2.1]heptane skeleton as a substituent group, there may becontained monomers substituted with an endo-alkyl group as representedby the following formulas (L4-1-endo) to (L4-4-endo). For goodreactivity, an exo proportion of at least 50 mol % is preferred, with anexo proportion of at least 80 mol % being more preferred.

Herein R^(L41) is as defined above.

Illustrative examples of the acid labile group of formula (L4) are givenbelow

Examples of the tertiary C₄-C₂₀ alkyl, tri(C₁-C₆-alkyl)silyl and C₄-C₂₀oxoalkyl groups included in the acid labile groups represented by R⁰¹⁵are as exemplified above for R^(L04).

While the polymer to be added to the resist composition of the inventioncomprises recurring units “a,” (b-1), and (b-2) in formula (1), andoptionally recurring units (b-3) in formula (2), additional recurringunits “c” having a carboxyl group may be copolymerized in the additivepolymer, if desired, for the purpose of improving alkali solubility andhydrophilicity of resist following development. Examples of therecurring units “c” having a carboxyl group are given below.

While the polymer to be added to the resist composition of the inventioncomprises recurring units “a,” (b-1), and (b-2) in formula (1), andoptionally recurring units (b-3) in formula (2), additional recurringunits “d” having an adhesive group of lactone and/or recurring units “e”having an acid labile group may be copolymerized in the additivepolymer, if desired, for the purpose of improving the miscibilitythereof with the base polymer in the resist composition and/orinhibiting film slimming on the resist surface. The recurring units “d”having an adhesive group of lactone and the recurring units “e” havingan acid labile group may be selected from those units used in the basepolymer, which will be described later.

Desirably the polymer having formula (1) or (2) has a weight averagemolecular weight (Mw) of about 1,000 to about 100,000, and especiallyabout 2,000 to about 30,000, as determined by gel permeationchromatography (GPC) using polystyrene standards. The Mw of the polymeris not limited thereto. A polymer with Mw of at least 1,000 exertssufficient barrier property against water during immersion lithographyand is effective for preventing photoresist components from beingleached with water. A polymer with Mw of up to 100,000 has asufficiently high rate of dissolution in an alkaline developer,minimizing the risk that when a resist film having the polymerincorporated therein is patterned, resin residues are left attached tothe substrate.

When used in the resist composition, the polymers comprising recurringunits “a,” (b-1), and (b-2) in formula (1) may be compounded alone or asa mixture in any desired proportion of two or more polymers havingdifferent copolymerization ratio or molecular weight or obtained throughcopolymerization of distinct monomers.

Likewise, when used in the resist composition, the polymers comprisingrecurring units “a,” (b-1), (b-2), and (b-3) in formula (2) may becompounded alone or as a mixture in any desired proportion of two ormore polymers having different copolymerization ratio or molecularweight or obtained through copolymerization of distinct monomers.

The subscripts “a,” (b-1), and (b-2) in formula (1) representative ofcopolymerization ratios (on a molar basis) of the corresponding unitsare in the range: 0<a<1.0, 0≦(b-1)<1.0, 0≦(b-2)<1.0, 0<(b-1)+(b-2)<1.0,and 0.5≦a+(b-1)+(b-2)≦1.0, and preferably 0<a<0.9, 0≦(b-1)<0.9,0≦(b-2)<0.9, 0.1≦(b-1)+(b-2)≦0.9, and 0.6≦a+(b-1)+(b-2)≦1.0.

The subscripts “a,” (b-1), (b-2), and (b-3) in formula (2)representative of copolymerization ratios (on a molar basis) of thecorresponding units are in the range: 0<a<1.0, 0≦(b-1)<1.0, 0≦(b-2)<1.0,0≦(b-1)+(b-2)<1.0, 0<(b-3)<1.0, and 0.5≦a+(b-1)+(b-2)+(b-3)≦1.0, andpreferably 0<a<0.9, 0≦(b-1)<0.9, 0≦(b-2)<0.9, 0≦(b-1)+(b-2)≦0.9,0.1<(b-3)<0.9, and 0.6≦a+(b-1)+(b-2)+(b-3)≦1.0.

The additional recurring units “c,” “d” and “e”, when copolymerized withthe recurring units in formula (1), may be present in the range:0≦c≦0.8, more specifically 0≦c≦0.7, 0≦d≦0.8, more specifically 0≦d≦0.7,and 0≦e≦0.8, more specifically 0≦e≦0.7, provided thata+(b-1)+(b-2)+c+d+e=1.

The additional recurring units “c”, “d” and “e”, when copolymerized withthe recurring units in formula (2), may be present in the range:0≦c≦0.8, more specifically 0≦c≦0.7, 0≦d≦0.8, more specifically 0≦d≦0.7,and 0≦e≦0.8, more specifically 0≦e≦0.7, provided thata+(b-1)+(b-2)+(b-3)+c+d+e=1.

It is noted that the meaning of a+(b-1)+(b-2)=1 is that in a polymercomprising recurring units a, (b-1), and (b-2), the sum of recurringunits a, (b-1) and (b-2) is 100 mol % based on the total amount ofentire recurring units. The meaning of a+(b-1)+(b-2)<1 is that the sumof recurring units a, (b-1), and (b-2) is less than 100 mol % based onthe total amount of entire recurring units, indicating the inclusion ofother recurring units.

In the resist composition of the invention, the polymeric surfactant(s)of formula (1) or (2) may be compounded in a total amount of 0.01 to 50parts by weight, and preferably 0.1 to 10 parts by weight per 100 partsby weight of the base resin. At least 0.01 phr of the polymer iseffective in improving the receding contact angle with water of thephotoresist film at its surface. Up to 50 phr of the polymer iseffective in forming a photoresist film having a low rate of dissolutionin an alkaline developer and capable of maintaining the height of a finepattern formed is therein.

The resist composition of the invention is advantageously used as achemically amplified positive or negative resist composition. Inaddition to the polymeric surfactant (B) described above, the chemicallyamplified positive resist composition generally comprises at least abase resin (A), specifically a base resin comprising recurring unitshaving acid labile groups and recurring units having hydroxy groupsand/or adhesive groups of lactone ring.

Since the base resin includes recurring units having hydroxy groupsand/or adhesive groups of lactone ring, the chemically amplifiedpositive resist composition ensures tight adhesion to a substrate. Sincethe base resin includes recurring units having acid labile groups, theacid labile groups are deprotected with the acid generated by the acidgenerator during exposure so that the exposed area of resist isconverted to be soluble in a developer, ensuring that a pattern isformed at a very high precision.

Base Resin

Suitable base resins include, but are not limited to, those polymerscomprising units of the following formula (R1) and/or (R2) and having aweight average molecular weight (Mw) of about 1,000 to about 100,000,especially about 3,000 to about 30,000, as measured by GPC versuspolystyrene standards.

Herein, R⁰⁰¹ is hydrogen, methyl or —CH₂CO₂R⁰⁰³.

R⁰⁰² is hydrogen, methyl or —CO₂R⁰⁰³.

R⁰⁰³ is a straight, branched or cyclic C₁-C₁₅ alkyl group, for example,methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,tert-amyl, n-pentyl, n-hexyl, cyclopentyl, cyclohexyl, ethylcyclopentyl,butylcyclopentyl, ethylcyclohexyl, butylcyclohexyl, adamantyl,ethyladamantyl, and butyladamantyl.

R⁰⁰⁴ is hydrogen or a monovalent C₁-C₁₅ hydrocarbon group having atleast one of fluorinated substituent groups, carboxyl groups andhydroxyl groups, for example, hydrogen, carboxyethyl, carboxybutyl,carboxycyclopentyl, carboxycyclohexyl, carboxynorbornyl,carboxyadamantyl, hydroxyethyl, hydroxybutyl, hydroxycyclopentyl,hydroxycyclohexyl, hydroxynorbornyl, hydroxyadamantyl,hydroxyhexafluoroisopropylcyclohexyl, anddi(hydroxyhexafluoroisopropyl)cyclohexyl.

At least one of R⁰⁰⁵ to R⁰⁰⁸ represents a monovalent C₁-C₁₅ hydrocarbongroup having at least one of fluorinated substituent groups, carboxylgroups and hydroxyl groups while the remaining R's independentlyrepresent hydrogen or straight, branched or cyclic C₁-C₁₅ alkyl groups.Examples of the monovalent C₁-C₁₅ hydrocarbon group having at least oneof fluorinated substituent groups, carboxyl groups and hydroxyl groupsinclude carboxy, carboxymethyl, carboxyethyl, carboxybutyl,hydroxymethyl, hydroxyethyl, hydroxybutyl, 2-carboxyethoxycarbonyl,4-carboxybutoxycarbonyl, 2-hydroxyethoxycarbonyl,4-hydroxybutoxycarbonyl, carboxycyclopentyloxycarbonyl,carboxycyclohexyloxycarbonyl, carboxynorbornyloxycarbonyl,carboxyadamantyloxycarbonyl, hydroxycyclopentyloxycarbonyl,hydroxycyclohexyloxycarbonyl, hydroxynorbornyloxycarbonyl,hydroxyadamantyloxycarbonyl,hydroxyhexafluoroisopropylcyclohexyloxycarbonyl, anddi(hydroxyhexafluoroisopropyl)cyclohexyloxycarbonyl. Examples of thestraight, branched or cyclic C₁-C₁₅ alkyl group are the same asexemplified for R⁰⁰³.

Alternatively, two of R⁰⁰⁵ to R⁰⁰⁸ (e.g., R⁰⁰⁵ and R⁰⁰⁶, or R⁰⁰⁶ andR⁰⁰⁷) may bond together to form a ring with the carbon atom(s) to whichthey are attached. In that event, at least one of ring-forming R⁰⁰⁵ toR⁰⁰⁸ is a divalent C₁-C₁₅ hydrocarbon group having at least one offluorinated substituent groups, carboxyl groups and hydroxyl groups,while the remaining are independently a single bond or a straight,branched or cyclic C₁-C₁₅ alkylene group. Examples of the divalentC₁-C₁₅ hydrocarbon group having at least one of fluorinated substituentgroups, carboxyl groups and hydroxyl groups include the groupsexemplified as the monovalent hydrocarbon group having at least one offluorinated substituent groups, carboxyl groups and hydroxyl groups,with one hydrogen atom eliminated therefrom. Examples of the straight,branched or cyclic C₁-C₁₅ alkylene groups include the groups exemplifiedfor R⁰⁰³, with one hydrogen atom eliminated therefrom.

R⁰⁰⁹ is a monovalent C₃-C₁₅ hydrocarbon group containing a —CO₂— partialstructure, for example, 2-oxooxolan-3-yl, 4,4-dimethyl-2-oxooxolan-3-yl,4-methyl-2-oxooxan-4-yl, 2-oxo-1,3-dioxolan-4-ylmethyl, and5-methyl-2-oxooxolan-5-yl.

At least one of R⁰¹⁰ to R⁰¹³ is a monovalent C₂-C₁₅ hydrocarbon groupcontaining a —CO₂— partial structure, while the remaining R's areindependently hydrogen or straight, branched or cyclic C₁-C₁₅ alkylgroups. Examples of the monovalent C₂-C₁₅ hydrocarbon group containing a—CO₂— partial structure include 2-oxooxolan-3-yloxycarbonyl,4,4-dimethyl-2-oxooxolan-3-yloxycarbonyl,4-methyl-2-oxooxan-4-yloxycarbonyl,2-oxo-1,3-dioxolan-4-ylmethyloxycarbonyl, and5-methyl-2-oxooxolan-5-yloxycarbonyl. Examples of the straight, branchedor cyclic C₁-C₁₅ alkyl groups are the same as exemplified for R⁰⁰³.

Alternatively, two of R⁰¹⁰ to R⁰¹³ (e.g., R⁰¹⁰ and R⁰¹¹, or R⁰¹¹ andR⁰¹²) may bond together to form a ring with the carbon atom(s) to whichthey are attached. In that event, at least one of ring-forming R⁰¹⁰ toR⁰¹³ is a divalent C₁-C₁₅ hydrocarbon group containing a —CO₂— partialstructure, while the remaining are independently a single bond or astraight, branched or cyclic C₁-C₁₅ alkylene group. Examples of thedivalent C₁-C₁₅ hydrocarbon group containing a —CO₂— partial structureinclude 1-oxo-2-oxapropane-1,3-diyl, 1,3-dioxo-2-oxapropane-1,3-diyl,1-oxo-2-oxabutane-1,4-diyl, and 1,3-dioxo-2-oxabutane-1,4-diyl, as wellas the groups exemplified as the monovalent hydrocarbon group containinga —CO₂— partial structure, with one hydrogen atom eliminated therefrom.Examples of the straight, branched or cyclic C₁-C₁₅ alkylene groupsinclude the groups exemplified for R⁰⁰³, with one hydrogen atomeliminated therefrom.

R⁰¹⁴ is a polycyclic C₇-C₁₅ hydrocarbon group or an alkyl groupcontaining a polycyclic hydrocarbon group, for example, norbornyl,bicyclo[3.3.1]nonyl, tricyclo[5.2.1.0^(2,6)]decyl, adamantyl,ethyladamantyl, butyladamantyl, norbornylmethyl, and adamantylmethyl.

R⁰¹⁵ is an acid labile group, which will be described later.

X is —CH₂ or an oxygen atom.

The subscript k is 0 or 1.

The acid labile groups represented by R⁰¹⁵ may be selected from avariety of such groups. Examples of the acid labile group are groups ofthe following general formulae (L1) to (L4), tertiary alkyl groups of 4to 20 carbon atoms, preferably 4 to 15 carbon atoms, trialkylsilylgroups in which each alkyl moiety has 1 to 6 carbon atoms, and oxoalkylgroups of 4 to 20 carbon atoms.

The broken line indicates a valence bond.

In formula (L1), R^(L01) and R^(L02) are hydrogen or straight, branchedor cyclic alkyl groups of 1 to 18 carbon atoms, preferably 1 to 10carbon atoms. Examples include hydrogen, methyl, ethyl, propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, cyclopentyl, cyclohexyl,2-ethylhexyl, n-octyl, and adamantyl. R^(L03) is a monovalenthydrocarbon group of 1 to 18 carbon atoms, preferably 1 to 10 carbonatoms, which may contain a hetero atom such as oxygen, examples of whichinclude unsubstituted straight, branched or cyclic alkyl groups andstraight, branched or cyclic alkyl groups in which some hydrogen atomsare replaced by hydroxyl, alkoxy, oxo, amino, alkylamino or the like.Examples of the straight, branched or cyclic alkyl groups are asexemplified above for R^(L01) and R^(L02), and examples of thesubstituted alkyl groups are shown below.

A pair of R^(L01) and R^(L02), R^(L01) and R^(L03), or R^(L02) andR^(L03) may bond together to form a ring with the carbon and oxygenatoms to which they are attached. Each of R^(L01), R^(L02) and R^(L03)is a straight or branched alkylene group of 1 to 18 carbon atoms,preferably 1 to 10 carbon atoms when they form a ring.

In formula (L2), R^(L04) is a tertiary alkyl group of 4 to 20 carbonatoms, preferably 4 to 15 carbon atoms, a trialkylsilyl group in whicheach alkyl moiety has 1 to 6 carbon atoms, an oxoalkyl group of 4 to 20carbon atoms, or a group of formula (L1). Exemplary tertiary alkylgroups are tert-butyl, tert-amyl, 1,1-diethylpropyl,2-cyclopentylpropan-2-yl, 2-cyclohexylpropan-2-yl,2-(bicyclo[2.2.1]heptan-2-yl)propan-2-yl, 2-(adamantan-1-yl)propan-2-yl,1-ethylcyclopentyl, 1-butylcyclopentyl, 1-ethylcyclohexyl,1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl, 1-ethyl-2-cyclohexenyl,2-methyl-2-adamantyl, and 2-ethyl-2-adamantyl. Exemplary trialkylsilylgroups are trimethylsilyl, triethylsilyl, and dimethyl-tert-butylsilyl.Exemplary oxoalkyl groups are 3-oxocyclohexyl, 4-methyl-2-oxooxan-4-yl,and 5-methyl-2-oxcoxolan-5-yl. In formula (L2), y is an integer of 0 to6.

In formula (L3), R^(L05) is a substituted or unsubstituted, straight,branched or cyclic C₁-C₁₀ alkyl group or a substituted or unsubstitutedC₆-C₂₀ aryl group. Examples of the substituted or unsubstituted alkylgroups include straight, branched or cyclic ones such as methyl, ethyl,propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl,n-hexyl, cyclopentyl, cyclohexyl and bicyclo[2.2.1]heptyl; substitutedforms of the foregoing in which some hydrogen atoms are replaced byhydroxyl, alkoxy, carboxy, alkoxycarbonyl, oxo, amino, alkylamino,cyano, mercapto, alkylthio, sulfo or other groups; and substituted formsof the foregoing in which some of the methylene groups are replaced byoxygen or sulfur atoms. Exemplary substituted or unsubstituted arylgroups are phenyl, methylphenyl, naphthyl, anthryl, phenanthryl, andpyrenyl. In formula (L3), m is 0 or 1, n is 0, 1, 2 or 3, and 2m+n isequal to 2 or 3.

In formula (L4), R^(L06) is a substituted or unsubstituted, straight,branched or cyclic C₁-C₁₀ alkyl group or a substituted or unsubstitutedC₆-C₂₀ aryl group. Examples of these groups are the same as exemplifiedfor R^(L05). R^(L07) to R^(L16) independently represent hydrogen ormonovalent C₁-C₁₅ hydrocarbon groups. Exemplary hydrocarbon groups arestraight, branched or cyclic alkyl groups such as methyl, ethyl, propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl,n-octyl, n-nonyl, n-decyl, cyclopentyl, cyclohexyl, cyclopentylmethyl,cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyland cyclohexylbutyl, and substituted forms of the foregoing in whichsome hydrogen atoms are replaced by hydroxyl, alkoxy, carboxy,alkoxycarbonyl, oxo, amino, alkylamino, cyano, mercapto, alkylthio,sulfo or other groups. Alternatively, two of R^(L07) to R^(L16) may bondtogether to form a ring with the carbon atom to which they are attached(for example, a pair of R^(L07) and R^(L08), R^(L07) and R^(L09),R^(L08) and R^(L10), R^(L09) and R^(L10), R^(L11) and R^(L12), R^(L13)and R^(L14), or a similar pair form a ring). Each of R^(L07) to R^(L16)represents a divalent C₁-C₁₅ hydrocarbon group when they form a ring,examples of which are the ones exemplified above for the monovalenthydrocarbon groups, with one hydrogen atom being eliminated. Two ofR^(L07) to R^(L16) which are attached to vicinal carbon atoms (forexample, a pair of R^(L07) and R^(L09), R^(L09) and R^(L15), R^(L13) andR^(R15), or a similar pair) may bond together directly to form a doublebond.

Of the acid labile groups of formula (L1), the straight and branchedones are exemplified by the following groups.

Of the acid labile groups of formula (L1), the cyclic ones are, forexample, tetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl,tetrahydropyran-2-yl, and 2-methyltetrahydropyran-2-yl.

Examples of the acid labile groups of formula (L2) includetert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-amyloxycarbonyl,tert-amyloxycarbonylmethyl, 1,1-diethylpropyloxycarbonyl,1,1-diethylpropyloxycarbonylmethyl, 1-ethylcyclopentyloxycarbonyl,1-ethylcyclopentyloxycarbonylmethyl, 1-ethyl-2-cyclopentenyloxycarbonyl,1-ethyl-2-cyclopentenyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl,2-tetrahydropyranyloxycarbonylmethyl, and2-tetrahydrofuranyloxycarbonylmethyl groups.

Examples of the acid labile groups of formula (L3) include1-methylcyclopentyl, 1-ethylcyclopentyl, 1-n-propylcyclopentyl,1-isopropylcyclopentyl, 1-n-butylcyclopentyl, 1-sec-butylcyclopentyl,1-cyclohexylcyclopentyl, 1-(4-methoxy-n-butyl)cyclopentyl,1-(bicyclo[2.2.1]heptan-2-yl)cyclopentyl,1-(7-oxabicyclo[2.2.1]heptan-2-yl)cyclopentyl, 1-methylcyclohexyl,1-ethylcyclohexyl, 3-methyl-1-cyclopenten-3-yl,3-ethyl-1-cyclopenten-3-yl, 3-methyl-1-cyclohexen-3-yl, and3-ethyl-1-cyclohexen-3-yl groups.

The acid labile groups of formula (L4) are preferably groups of thefollowing formulae (L4-1) to (L4-4).

In formulae (L4-1) to (L4-4), the broken line indicates a bonding siteand direction. R^(L41) is each independently selected from monovalenthydrocarbon groups, typically straight, branched or cyclic C₁-C₁₀ alkylgroups, for example, methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl, andcyclohexyl.

For formulas (L4-1) to (L4-4), there can exist enantiomers anddiastereomers. Each of formulae (L4-1) to (L4-4) collectively representsall such stereoisomers. Such stereoisomers may be used alone or inadmixture.

For example, the general formula (L4-3) represents one or a mixture oftwo selected from groups having the following general formulas (L4-3-1)and (L4-3-2).

Herein R^(L41) is as defined above.

Similarly, the general formula (L4-4) represents one or a mixture of twoor more selected from groups having the following general formulas(L4-4-1) to (L4-4-4).

Herein R^(L41) is as defined above.

Each of formulas (L4-1) to (L4-4), (L4-3-1) and (L4-3-2), and (L4-4-1)to (L4-4-4) collectively represents an enantiomer thereof and a mixtureof enantiomers.

It is noted that in the above formulas (L4-1) to (L4-4), (L4-3-1) and(L4-3-2), and (L4-4-1) to (L4-4-4), the bond direction is on the exoside relative to the bicyclo[2.2.1]heptane ring, which ensures highreactivity for acid catalyzed elimination reaction (see JP-A2000-336121). In preparing these monomers having a tertiary exo-alkylgroup of bicyclo[2.2.1]heptane skeleton as a substituent group, theremay be contained monomers substituted with an endo-alkyl group asrepresented by the following formulas (L4-1-endo) to (L4-4-endo). Forgood reactivity, an exo proportion of at least 50 mol % is preferred,with an exo proportion of at least 80 mol % being more preferred.

Herein R^(L41) is as defined above.

Illustrative examples of the acid labile group of formula (L4) are givenbelow.

Examples of the tertiary C₄-C₂₀ alkyl, tri(C₁-C₆-alkyl)silyl and C₄-C₂₀oxoalkyl groups included in the acid labile groups represented by R⁰¹⁵are as exemplified above for R^(L04).

In formula (R2), R⁰¹⁶ and R⁰¹⁸ each are hydrogen or methyl. R⁰¹⁷ is astraight, branched or cyclic C₁-C₈ alkyl group.

In formula (R1), the subscripts a1′, a2′, a3′, b1′, b2′, b3′, c1′, c2′,c3′, d1′, d2′, d3′, and e′ are numbers from 0 to less than 1, satisfyinga1′+a2′+a3′+b1′+b2′+b3′+c1′+c2′+c3′+d1′+d2′+d3′+e′=1. In formula (R2),f′, g′, h′, i′, j′, k′, l′, and m′ are numbers from 0 to less than 1,satisfying f′+g′+h′+i′+j′+k′+l′+m′=1; x′, y′ and z′ are each an integerof 0 to 3, satisfying 1≦x′+y′+z′≦5 and 1≦y′+z′≦3. In addition, one ormore monomers selected from indenes, norbornadienes, acenaphthylenes andvinyl ethers may be copolymerized.

It is noted that the preferred base resins used in negative resistcompositions include those of formulae (R1) and (R2) wherein d1′, d2′,d3′, g′, and m′ are 0, but are not limited thereto.

Examples of the recurring units incorporated at compositional ratio allin formula (R1) are shown below, though not limited thereto.

Examples of the recurring units incorporated at compositional ratio b1′in formula (R1) are shown below, though not limited thereto.

Examples of the recurring units incorporated at compositional ratio d1′in formula (R1) are shown below, though not limited thereto.

Examples of polymers comprising recurring units in compositional ratiosa3′, b3′, c3′ and d3′ in formula (R1) are shown below, though notlimited thereto.

Furthermore, recurring units having a photosensitive sulfonium salt asrepresented by the general formula (PA) may be copolymerized with (R1)and/or (R2) and incorporated in the polymers.

Herein R^(p1) is hydrogen or methyl. R^(p2) is a phenylene group,—O—R^(p5)— or —C(═O)—X—R^(p5)— wherein X is an oxygen atom or NH, andR^(p5) is a straight, branched or cyclic C₁-C₆ alkylene, alkenylene orphenylene group which may contain a carbonyl, ester or ether group.R^(p3) and R^(p4) are each independently a straight, branched or cyclicC₁-C₁₂ alkyl group which may contain a carbonyl, ester or ether group,or a C₆-C₁₂ aryl group, C₇-C₂₀ aralkyl group or thiophenyl group. X is anon-nucleophilic counter ion,

The polymer used as the base resin is not limited to one type and amixture of two or more polymers may be added. The use of plural polymersallows for easy adjustment of resist properties.

Acid Generator

In the resist composition of the invention, an acid generator,specifically a compound capable of generating an acid in response toactinic light or radiation may be included in order that the resistcomposition function as a chemically amplified positive resistcomposition. The acid generator may be any compound capable ofgenerating an acid upon exposure of high-energy radiation, which isgenerally referred to as “photoacid generator” or PAG. Suitablephotoacid generators include sulfonium salts, iodonium salts,sulfonyldiazomethane, N-sulfonyloxyimide, and oxime-O-sulfonate acidgenerators. Exemplary acid generators are given below while they may beused alone or in admixture of two or more.

Sulfonium salts are salts of sulfonium cations with sulfonates,bis(substituted alkylsulfonyl)imides and tris(substitutedalkylsulfonyl)methides. Exemplary sulfonium cations includetriphenylsulfonium, (4-tert-butoxyphenyl)diphenylsulfonium,bis(4-tert-butoxyphenyl)phenylsulfonium,tris(4-tert-butoxyphenyl)sulfonium,(3-tert-butoxyphenyl)diphenylsulfonium,bis(3-tert-butoxyphenyl)phenylsulfonium,tris(3-tert-butoxyphenyl)sulfonium,(3,4-di-tert-butoxyphenyl)diphenylsulfonium,bis(3,4-di-tert-butoxyphenyl)phenylsulfonium,tris(3,4-di-tert-butoxyphenyl)sulfonium,diphenyl(4-thiophenoxyphenyl)sulfonium,(4-tert-butoxycarbonylmethyloxyphenyl)diphenylsulfonium,tris(4-tert-butoxycarbonylmethyloxyphenyl)sulfonium,(4-tert-butoxyphenyl)bis(4-dimethylaminophenyl)sulfonium,tris(4-dimethylaminophenyl)sulfonium, 2-naphthyldiphenylsulfonium,dimethyl-2-naphthylsulfonium, 4-hydroxyphenyldimethylsulfonium,4-methoxyphenyldimethylsulfonium, trimethylsulfonium,2-oxocyclohexylcyclohexylmethylsulfonium, trinaphthylsulfonium,tribenzylsulfonium, diphenylmethylsulfonium, dimethylphenylsulfonium,2-oxo-2-phenylethylthiacyclopentanium,4-n-butoxynaphthyl-1-thiacyclopentanium, and2-n-butoxynaphthyl-1-thiacyclopentanium.

Exemplary sulfonates include trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, mesitylenesulfonate,2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate,4-(4′-toluenesulfonyloxy)benzenesulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropane-sulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropane-sulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.

Exemplary bis(substituted alkylsulfonyl)imides includebistrifluoromethylsulfonylimide, bispentafluoroethylsulfonylimide,bisheptafluoropropylsulfonylimide, and 1,3-propylenebissulfonylimide. Atypical tris(substituted alkylsulfonyl)methide istristrifluoromethylsulfonylmethide. Sulfonium salts based on combinationof the foregoing examples are included.

Iodonium salts are salts of iodonium cations with sulfonates,bis(substituted alkylsulfonyl)imides and tris(substitutedalkylsulfonyl)methides. Exemplary iodonium cations are aryliodoniumcations including diphenyliodinium, bis(4-tert-butylphenyl)iodonium,4-tert-butoxyphenylphenyliodonium, and 4-methoxyphenylphenyliodonium.Exemplary sulfonates include trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, mesitylenesulfonate,2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate,4-(4-toluenesulfonyloxy)benzenesulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropane-sulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropane-sulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.

Exemplary bis(substituted alkylsulfonyl)imides includebistrifluoromethylsulfonylimide, bispentafluoroethylsulfonylimide,bisheptafluoropropylsulfonylimide, and 1,3-propylenebissulfonylimide.

A typical tris(substituted alkylsulfonyl)methide istristrifluoromethylsulfonylmethide. Iodonium salts based on combinationof the foregoing examples are included.

Exemplary sulfonyldiazomethane compounds include bissulfonyldiazomethanecompounds and sulfonyl-carbonyldiazomethane compounds such asbis(ethylsulfonyl)diazomethane, bis(1-methylpropylsulfonyl)diazomethane,bis(2-methylpropylsulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane,bis(perfluoroisopropylsulfonyl)diazomethane,bis(phenylsulfonyl)diazomethane,bis(4-methylphenylsulfonyl)diazomethane,bis(2,4-dimethylphenylsulfonyl)diazomethane,bis(2-naphthylsulfonyl)diazomethane,bis(4-acetyloxyphenylsulfonyl)diazomethane,bis(4-methanesulfonyloxyphenylsulfonyl)diazomethane,bis(4-(4-toluenesulfonyloxy)phenylsulfonyl)diazomethane,bis(4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(3,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-5-isopropyl-4-(n-hexyloxy)phenylsulfonyl)diazo-methane,4-methylphenylsulfonylbenzoyldiazomethane,tert-butylcarbonyl-4-methylphenylsulfonyldiazomethane,2-naphthylsulfonylbenzoyldiazomethane,4-methylphenylsulfonyl-2-naphthoyldiazomethane,methylsulfonylbenzoyldiazomethane, andtert-butoxycarbonyl-4-methylphenylsulfonyldiazomethane.

N-sulfonyloxyimide photoacid generators include combinations of imideskeletons with sulfonates. Exemplary imide skeletons are succinimide,naphthalene dicarboxylic acid imide, phthalimide, cyclohexyldicarboxylicacid imide, 5-norbornene-2,3-dicarboxylic acid imide, and7-oxabicyclo[2.2.1]-5-heptene-2,3-dicarboxylic acid imide.

Exemplary sulfonates include trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, mesitylenesulfonate,2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate, 1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropane-sulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropane-sulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl) ethanesulfonate.

Benzoinsulfonate photoacid generators include benzoin tosylate, benzoinmesylate, and benzoin butanesulfonate.

Pyrogallol trisulfonate photoacid generators include pyrogallol,phloroglucinol, catechol, resorcinol, and hydroquinone compounds, inwhich all the hydroxyl groups are substituted bytrifluoromethanesulfonate, pentafluoroethanesulfonate,nonafluorobutanesulfonate, dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropane-sulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropane-sulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2 hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.

Nitrobenzyl sulfonate photoacid generators include 2,4-dinitrobenzylsulfonate, 2-nitrobenzyl sulfonate, and 2,6-dinitrobenzyl sulfonate,with exemplary sulfonates including trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropane-sulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropane-sulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.Also useful are analogous nitrobenzyl sulfonate compounds in which thenitro group on the benzyl side is substituted by a trifluoromethylgroup.

Sulfone photoacid generators include bis(phenylsulfonyl)methane,bis(4-methylphenylsulfonyl)methane, bis(2-naphthylsulfonyl)methane,2,2-bis(phenylsulfonyl)propane, 2,2-bis(4-methylphenylsulfonyl)propane,2,2-bis(2-naphthylsulfonyl)propane,2-methyl-2-(p-toluenesulfonyl)propiophenone,2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane, and2,4-dimethyl-2-(p-toluenesulfonyl)pentan-3-one.

Photoacid generators in the form of glyoxime derivatives are describedin Japanese Patent No. 2,906,999 and JP-A 9-301948 and includebis-O-(p-toluenesulfonyl)-α-dimethylglyoxime,bis-O-(p-toluenesulfonyl)-α-diphenylglyoxime,bis-O-(p-toluenesulfonyl)-α-dicyclohexylglyoxime,bis-O-(p-toluenesulfonyl)-2,3-pentanedioneglyoxime,bis-O-(n-butanesulfonyl)--α-dimethylglyoxime,bis-O-(n-butanesulfonyl)-α-diphenylglyoxime, bis-O-(n-butanesulfonyl)-α-dicyclohexylglyoxime, bis-O-(methanesulfonyl)-α-dimethylglyoxime,bis-O-(trifluoromethanesulfonyl)-α-dimethylglyoxime,bis-O-(2,2,2-trifluoroethanesulfonyl) -α-dimethylglyoxime,bis-O-(10-camphorsulfonyl)-α-dimethylglyoxime,bis-O-(benzenesulfonyl)-α-dimethylglyoxime,bis-O-(p-fluorobenzenesulfonyl)-α-dimethylglyoxime,bis-O-(p-trifluoromethylbenzenesulfonyl)-α-dimethylglyoxime,bis-O-(xylenesulfonyl)-α-dimethylglyoxime,bis-O-(trifluoromethanesulfonyl)-nioxime,bis-O-(2,2,2-trifluoroethanesulfonyl)-nioxime,bis-O-(10-camphorsulfonyl)-nioxime, bis-O-(benzenesulfonyl)-nioxime,bis-O-(p-fluorobenzenesulfonyl)-nioxime,bis-O-(p-trifluoromethylbenzenesulfonyl)-nioxime, andbis-O-(xylenesulfonyl)-nioxime.

Also included are the oxime sulfonates described in U.S. Pat. No.6,004,724, for example,(5-(4-toluenesulfonyl)oxyimino-5H-thiophen-2-ylidene)phenyl-acetonitrile,(5-(10-camphorsulfonyl)oxyimino-5H-thiophen-2-ylidene)phenyl-acetonitrile,(5-n-octanesulfonyloxyimino-5H-thiophen-2-ylidene)phenyl-acetonitrile,(5-(4-toluenesulfonyl)oxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile,(5-(10-camphorsulfonyl)oxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile,(5-n-octanesulfonyloxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile,etc.

Also included are the oxime sulfonates described in U.S. Pat. No.6,916,591, for example,(5-(4-(4-toluenesulfonyloxy)benzenesulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrileand(5-(2,5-bis(4-toluenesulfonyloxy)benzenesulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrile.

Also included are the oxime sulfonates described in U.S. Pat. No.6,261,738 and JP-A 2000-314956, for example,2,2,2-trifluoro-1-phenyl-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(10-camphoryl-sulfonate);2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(4-methoxyphenylsulfonate);2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(1-naphthylsulfonate);2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(2-naphthylsulfonate);2,2,2-trifluoro-1-phenyl-ethanoneoxime-O-(2,4,6-trimethylphenylsulfonate);2,2,2-trifluoro-1-(4-methylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(4-methylphenyl)-ethanone oxime-O-(methylsulfonate);2,2,2-trifluoro-1-(2-methylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(1-naphthylsulfonate);2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(2-naphthylsulfonate);2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(2,4,6-trimethyl-phenyl)-ethanoneoxime-O-(1-naphthylsulfonate);2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(2-naphthylsulfonate);2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(4-methylthiophenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(3,4-dimethoxyphenyl)-ethanoneoxime-O-methylsulfonate; 2,2,3,3,4,4,4-heptafluoro-1-phenyl-butanoneoxime-O-(10-camphorylsulfonate); 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-10-camphorylsulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(4-methoxyphenyl)sulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(1-naphthyl)-sulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(2,4,6-trimethylphenyl)sulfonate;2,2,2-trifluoro-1-(4-methylphenyl)-ethanoneoxime-O-(10-camphoryl)sulfonate;2,2,2-trifluoro-1-(4-methylphenyl)-ethanone oxime-O-methyl-sulfonate;2,2,2-trifluoro-1-(2-methylphenyl)-ethanoneoxime-O-(10-camphoryl)sulfonate;2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(1-naphthyl)sulfonate;2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate;2,2,2-trifluoro-1-(2,4,6-trimethyl-phenyl)-ethanoneoxime-O-(10-camphoryl)sulfonate;2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(1-naphthyl)sulfonate;2,2,2-trifluoro-1-(2,4,6-trimethyl-phenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(3,4-dimethoxyphenyl)-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanoneoxime-O-(4-methylphenyl)sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanoneoxime-O-(4-methoxyphenyl)sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanoneoxime-O-(4-dodecylphenyl)-sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-octylsulfonate;2,2,2-trifluoro-1-(4-thiomethyl-phenyl)-ethanoneoxime-O-(4-methoxyphenyl)sulfonate;2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanoneoxime-O-(4-dodecylphenyl)sulfonate;2,2,2-trifluoro-1-(4-thiomethyl-phenyl)-ethanone oxime-O-octylsulfonate;2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate;2,2,2-trifluoro-1-(2-methylphenyl)-ethanone oxime-O-methyl-sulfonate;2,2,2-trifluoro-1-(4-methylphenyl)ethanone oxime-O-phenylsulfonate;2,2,2-trifluoro-1-(4-chlorophenyl)-ethanone oxime-O-phenylsulfonate;2,2,3,3,4,4,4-heptafluoro-1-(phenyl)-butanoneoxime-O-(10-camphoryl)sulfonate; 2,2,2-trifluoro-1-naphthyl-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-2-naphthyl-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-[4-benzylphenyl]-ethanoneoxime-O-methylsulfonate;2,2,2-trifluoro-1-[4-(phenyl-1,4-dioxa-but-1-yl)phenyl]-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-naphthyl-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-2-naphthyl-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-1-[4-benzylphenyl]-ethanoneoxime-O-propyl-sulfonate;2,2,2-trifluoro-1-[4-methylsulfonylphenyl]-ethanoneoxime-O-propylsulfonate;1,3-bis[l-(4-phenoxy-phenyl)-2,2,2-trifluoroethanoneoxime-O-sulfonyl]phenyl;2,2,2-trifluoro-1-[4-methylsulfonyloxyphenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[4-methylcarbonyloxy-phenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[6H,7H-5,8-dioxonaphth-2-yl]-ethanoneoxime-O-propyl-sulfonate;2,2,2-trifluoro-1-[4-methoxycarbonyl-methoxyphenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[4-(methoxycarbonyl)-(4-amino-1-oxa-pent-1-yl)-phenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[3,5-dimethyl-4-ethoxyphenyl]-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-1-[4-benzyloxyphenyl]-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-1-[2-thiophenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[1-dioxa-thiophen-2-yl)]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(trifluoromethanesulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(trifluoromethane-sulfonate);2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(1-propanesulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)-ethanoneoxime(1-propanesulfonate); and2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(1-butanesulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(1-butanesulfonate).

Also included are the oxime sulfonates described in U.S. Pat. No.6,916,591, for example,2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(4-(4-methylphenylsulfonyloxy)phenylsulfonyloxy-imino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(4-(4-methylphenylsulfonyloxy)phenylsulfonate) and2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(2,5-bis(4-methylphenyl-sulfonyloxy)benzenesulfonyloxy)phenylsulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(2,5-bis(4-methylphenylsulfonyloxy)benzenesulfonyloxy)phenylsulfonate).

Also included are the oxime sulfonates described in JP-A 9-95479 andJP-A 9-230588 and the references cited therein, for example,α-(p-toluenesulfonyloxyimino)-phenylacetonitrile,α-(p-chlorobenzenesulfonyloxyimino)-phenylacetonitrile,α-(4-nitrobenzenesulfonyloxyimino)-phenylacetonitrile,α-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)-phenylacetonitrile,α-(benzenesulfonyloxyimino)-4-chlorophenylacetonitrile,α-(benzenesulfonyloxyimino)-2,4-dichlorophenylacetonitrile,α-(benzenesulfonyloxyimino)-2,6-dichlorophenylacetonitrile,α-(benzenesulfonyloxyimino)-4-methoxyphenylacetonitrile,α-(2-chlorobenzenesulfonyloxyimino)-4-methoxyphenylaceto-nitrile,α-(benzenesulfonyloxyimino)-2-thienylacetonitrile,α-(4-dodecylbenzenesulfonyloxyimino)-phenylacetonitrile,α-[(4-toluenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-[(dodecylbenzenesulfonyloxyimino)-4-methoxyphenyl]aceto-nitrile,α-(tosyloxyimino)-3-thienylacetonitrile,α-(methylsulfonyloxyimino)-1-cyclopentenylacetonitrile,α-(ethylsulfonyloxyimino)-1-cyclopentenylacetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclopentenylacetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclopentenylacetonitrile,α-(ethylsulfonyloxyimino)-1-cyclohexenylacetonitrile.α-(isopropylsulfonyloxyimino)-1-cyclohexenylacetonitrile, andα-(n-butylsulfonyloxyimino)-1-cyclohexenylacetonitrile.

Also included are oxime sulfonates having the following formula, asdescribed in WO 2004/074242.

Herein R^(s1) is a substituted or unsubstituted haloalkylsulfonyl orhalobenzenesulfonyl group of 1 to 10 carbon atoms, R^(s2) is a haloalkylgroup of 1 to 11 carbon atoms, and Ar^(s1) is substituted orunsubstituted aromatic or hetero-aromatic group. Examples include2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyl-oxyimino)-pentyl]-fluorene,2-[2,2,3,3,4,4-pentafluoro-1-(nonafluorobutylsulfonyloxy-imino)-butyl]-fluorene,2-[2,2,3,3,4,4,5,5,6,6-decafluoro-1-(nonafluorobutylsulfonyl-oxyimino)-hexyl]-fluorene,2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxy-imino)-pentyl]-4-biphenyl,2-[2,2,3,3,4,4-pentafluoro-1-(nonafluorobutylsulfonyloxy-imino)-butyl]-4-biphenyl,and2-[2,2,3,3,4,4,5,5,6,6-decafluoro-1-(nonafluorobutylsulfonyl-oxyimino)-hexyl]-4-biphenyl.

Suitable bisoxime sulfonates include those described in JP-A 9-208554,for example,bis(α-(4-toluenesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(benzenesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(methanesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(butanesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(10-camphorsulfonyloxy)imino)-p-phenylenediaceto-nitrile,bis(α-(trifluoromethanesulfonyloxy)imino)-p-phenylenediaceto-nitrile,bis(α-(4-methoxybenzenesulfonyloxy)imino)-p-phenylenediaceto-nitrile,bis(an(4-toluenesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(benzenesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(methanesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(butanesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(10-camphorsulfonyloxy)imino)-m-phenylenediaceto-nitrile,bis(α-(4-toluenesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(trifluoromethanesulfonyloxy)imino)-m-phenylenediaceto-nitrile,bis(α-(4-methoxybenzenesulfonyloxy)imino)-m-phenylenediaceto-nitrile,etc.

Of these, preferred photoacid generators are sulfonium salts,bissulfonyldiazomethanes, N-sulfonyloxyimides, oxime-O-sulfonates andglyoxime derivatives. More preferred photoacid generators are sulfoniumsalts, bissulfonyldiazomethanes, N-sulfonyloxyimides, andoxime-O-sulfonates. Typical examples include triphenylsulfoniump-toluenesulfonate, triphenylsulfonium camphorsulfonate,triphenylsulfonium pentafluorobenzenesulfonate, triphenylsulfoniumnonafluorobutanesulfonate, triphenylsulfonium4-(4′-toluenesulfonyloxy)benzenesulfonate, triphenylsulfonium2,4,6-triisopropylbenzenesulfonate, 4-tert-butoxyphenyldiphenylsulfoniump-toluenesulfonate, 4-tert-butoxyphenyldiphenylsulfoniumcamphorsultonate, 4-tert-butoxyphenyldiphenylsulfonium4-(4′-toluenesulfonyl-oxy)benzenesulfonate,tris(4-methylphenyl)sulfonium camphorsulfonate,tris(4-tert-butylphenyl)sulfonium camphorsulfonate,4-tert-butylphenyldiphenylsulfonium camphorsulfonate,4-tert-butylphenyldiphenylsulfonium nonafluoro-1-butane-sulfonate,4-tert-butylphenyldiphenylsulfoniumpentafluoroethyl-perfluorocyclohexanesulfonate,4-tert-butylphenyldiphenylsulfonium perfluoro-1-octane-sulfonate,triphenylsulfonium 1,1-difluoro-2-naphthyl-ethanesulfonate,triphenylsulfonium1,1,2,2-tetrafluoro-2-(norbornan-2-yl)-ethanesulfonate,bis(tert-butylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane,bis(2,4-dimethylphenylsulfonyl)diazomethane,bis(4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(3,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-5-isopropyl-4-(n-hexyloxy)phenylsulfonyl)diazo-methane,bis(4-tert-butylphenylsulfonyl)diazomethane,N-camphorsulfonyloxy-5-norbornene-2,3-dicarboxylic acid imide,N-p-toluenesulfonyloxy-5-norbornene-2,3-dicarboxylic acid imide,2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxy-imino)-pentyl]-fluorene,2-[2,2,3,3,4,4-pentafluoro-1-(nonafluorobutylsulfonyloxy-imino)-butyl]-fluorene,and2-[2,2,3,3,4,4,5,5,6,6-decafluoro-1-(nonafluorobutylsulfonyl-oxyimino)-hexyl]-fluorene.

In the chemically amplified resist composition, an appropriate amount ofthe photoacid generator is, but not limited to, 0.1 to 20 parts, andespecially 0.1 to 10 parts by weight per 100 parts by weight of the baseresin. If the amount of the PAG is up to 20 phr, the resultingphotoresist film has a sufficiently high transmittance to minimize arisk of degrading resolution. The PAG may be used alone or in admixtureof two or more. The transmittance of the resist film can be controlledby using a PAG having a low transmittance at the exposure wavelength andadjusting the amount of the PAG added.

In the resist composition, there may be added a compound which isdecomposed with an acid to generate another acid, that is,acid-amplifier compound. For these compounds, reference should be madeto J. Photopolym. Sci. and Tech., 8, 43-44, 45-46 (1995), and ibid., 9,29-30 (1996).

Examples of the acid-amplifier compound includetert-butyl-2-methyl-2-tosyloxymethyl acetoacetate and2-phenyl-2-(2-tosyloxyethyl)-1,3-dioxolane, but are not limited thereto.Of well-known photoacid generators, many of those compounds having poorstability, especially poor thermal stability exhibit an acidamplifier-like behavior.

In the resist composition, an appropriate amount of the acid-amplifiercompound is up to 2 parts, and preferably up to 1 part by weight per 100parts by weight of the base resin. Up to 2 phr of the acid-amplifiercompound allows for diffusion control, minimizing a risk of degradingresolution and pattern profile.

In addition to the base resin and PAG as well as the polymericsurfactant, the resist composition of the invention may further compriseat least one of an organic solvent, a basic compound, a dissolutionregulator, a crosslinker, and a surfactant.

Solvent

The organic solvent used herein may be any organic solvent in which thebase resin, acid generator, and other components are soluble.Illustrative, non-limiting, examples of the organic solvent includeketones such as cyclohexanone and methyl-2-n-amyl ketone; alcohols suchas 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol,and 1-ethoxy-2-propanol; ethers such as propylene glycol monomethylether, ethylene glycol monomethyl ether, propylene glycol monoethylether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether,and diethylene glycol dimethyl ether; esters such as propylene glycolmonomethyl ether acetate (PGMEA), propylene glycol monoethyl etheracetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate,tert-butyl propionate, and propylene glycol mono-tert-butyl etheracetate; and lactones such as γ-butyrolactone. These solvents may beused alone or in combinations of two or more thereof. Of the aboveorganic solvents, it is recommended to use diethylene glycol dimethylether, 1-ethoxy-2-propanol, propylene glycol monomethyl ether acetate,and mixtures thereof because the acid generator is most soluble therein.

An appropriate amount of the organic solvent used is about 200 to 3,000parts, especially about 400 to 2,500 parts by weight per 100 parts byweight of the base resin.

Basic Compound

In the resist composition, an organic nitrogen-containing compound orcompounds may be compounded as the basic compound. The organicnitrogen-containing compound used herein is preferably a compoundcapable of suppressing the rate of diffusion when the acid generated bythe acid generator diffuses within the resist film. The inclusion oforganic nitrogen-containing compound holds down the rate of aciddiffusion within the resist film, resulting in better resolution. Inaddition, it suppresses changes in sensitivity following exposure andreduces substrate and environment dependence, as well as improving theexposure latitude and the pattern profile.

Suitable organic nitrogen-containing compounds include primary,secondary, and tertiary aliphatic amines, mixed amines, aromatic amines,heterocyclic amines, nitrogen-containing compounds having carboxylgroup, nitrogen-containing compounds having sulfonyl group,nitrogen-containing compounds having hydroxyl group, nitrogen-containingcompounds having hydroxyphenyl group, alcoholic nitrogen-containingcompounds, amide derivatives, imide derivatives, and carbamatederivatives.

Examples of suitable primary aliphatic amines include ammonia,methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine,isobutylamine, sec-butylamine, tert-butylamine, pentylamine,tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine,heptylamine, octylamine, nonylamine, decylamine, dodecylamine,cetylamine, methylenediamine, ethylenediamine, andtetraethylenepentamine.

Examples of suitable secondary aliphatic amines include dimethylamine,diethylamine, di-n-propylamine, diisopropylamine, di-n-butylamine,diisobutylamine, di-sec-butylamine, dipentylamine, dicyclopentylamine,dihexylamine, dicyclohexylamine, diheptylamine, dioctylamine,dinonylamine, didecylamine, didodecylamine, dicetylamine,N,N-dimethylmethylenediamine, N,N-dimethylethylenediamine, andN,N-dimethyltetraethylenepentamine. Examples of suitable tertiaryaliphatic amines include trimethylamine, triethylamine,tri-n-propylamine, triisopropylamine, tri-n-butylamine,triisobutylamine, tri-sec-butylamine, tripentylamine,tricyclopentylamine, trihexylamine, tricyclohexylamine, triheptylamine,trioctylamine, trinonylamine, tridecylamine, tridodecylamine,tricetylamine, N,N,N′,N′-tetramethylmethylenediamine,N,N,N′,N′-tetramethylethylenediamine, andN,N,N′,N′-tetramethyltetraethylenepentamine.

Examples of suitable mixed amines include dimethylethylamine,methylethylpropylamine, benzylamine, phenethylamine, andbenzyldimethylamine. Examples of suitable aromatic and heterocyclicamines include aniline derivatives (e.g., aniline, N-methylaniline,N-ethylaniline, N-propylaniline, N,N-dimethylaniline, 2-methylaniline,3-methylaniline, 4-methylaniline, ethylaniline, propylaniline,trimethylaniline, 2-nitroaniline, 3-nitroaniline, 4-nitroaniline,2,4-dinitroaniline, 2,6-dinitroaniline, 3,5-dinitroaniline, andN,N-dimethyltoluidine), diphenyl(p-tolyl)amine, methyldiphenylamine,triphenylamine, phenylenediamine, naphthylamine, diaminonaphthalene,pyrrole derivatives (e.g., pyrrole, 2H-pyrrole, 1-methylpyrrole,2,4-dimethylpyrrole, 2,5-dimethylpyrrole, and N-methylpyrrole), oxazolederivatives (e.g., oxazole and isooxazole), thiazole derivatives (e.g.,thiazole and isothiazole), imidazole derivatives (e.g., imidazole,4-methylimidazole, and 4-methyl-2-phenylimidazole), pyrazolederivatives, furazan derivatives, pyrroline derivatives (e.g., pyrrolineand 2-methyl-1-pyrroline), pyrrolidine derivatives (e.g., pyrrolidine,N-methylpyrrolidine, pyrrolidinone, and N-methylpyrrolidone),imidazoline derivatives, imidazolidine derivatives, pyridine derivatives(e.g., pyridine, methylpyridine, ethylpyridine, propylpyridine,butylpyridine, 4-(1-butylpentyl)pyridine, dimethylpyridine,trimethylpyridine, triethylpyridine, phenylpyridine,3-methyl-2-phenylpyridine, 4-tert-butylpyridine, diphenylpyridine,benzylpyridine, methoxypyridine, butoxypyridine, dimethoxypyridine,4-pyrrolidinopyridine, 2-(1-ethylpropyl)pyridine, aminopyridine, anddimethylaminopyridine), pyridazine derivatives, pyrimidine derivatives,pyrazine derivatives, pyrazoline derivatives, pyrazolidine derivatives,piperidine derivatives, piperazine derivatives, morpholine derivatives,indole derivatives, isoindole derivatives, 1H-indazole derivatives,indoline derivatives, quinoline derivatives (e.g., quinoline and3-quinolinecarbonitrile), isoquinoline derivatives, cinnolinederivatives, quinazoline derivatives, quinoxaline derivatives,phthalazine derivatives, purine derivatives, pteridine derivatives,carbazole derivatives, phenanthridine derivatives, acridine derivatives,phenazine derivatives, 1,10-phenanthroline derivatives, adeninederivatives, adenosine derivatives, guanine derivatives, guanosinederivatives, uracil derivatives, and uridine derivatives.

Examples of suitable nitrogen-containing compounds having carboxyl groupinclude aminobenzoic acid, indolecarboxylic acid, and amino acidderivatives (e.g. nicotinic acid, alanine, alginine, aspartic acid,glutamic acid, glycine, histidine, isoleucine, glycylleucine, leucine,methionine, phenylalanine, threonine, lysine,3-aminopyrazine-2-carboxylic acid, and methoxyalanine)

Examples of suitable nitrogen-containing compounds having sulfonyl groupinclude 3-pyridinesulfonic acid and pyridinium p-toluenesulfonate.Examples of suitable nitrogen-containing compounds having hydroxylgroup, nitrogen-containing compounds having hydroxyphenyl group, andalcoholic nitrogen-containing compounds include 2-hydroxypyridine,aminocresol, 2,4-quinolinediol, 3-indolemethanol hydrate,monoethanolamine, diethanolamine, triethanolamine,N-ethyldiethanolamine, N,N-diethylethanolamine, triisopropanolamine,2,2′-iminodiethanol, 2-aminoethanol, 3-amino-1-propanol,4-amino-1-butanol, 4-(2-hydroxyethyl)morpholine,2-(2-hydroxyethyl)pyridine, 1-(2-hydroxyethyl)piperazine,1-[2-(2-hydroxyethoxy)ethyl]piperazine, piperidine ethanol,1-(2-hydroxyethyl)pyrrolidine, 1-(2-hydroxyethyl)-2-pyrrolidinone,3-piperidino-1,2-propanediol, 3-pyrrolidino-1,2-propanediol,8-hydroxyjulolidine, 3-quinuclidinol, 3-tropanol, 1-methyl-2-pyrrolidineethanol, 1-aziridine ethanol, N-(2-hydroxyethyl)phthalimide, andN-(2-hydroxyethyl)isonicotinamide. Examples of suitable amidederivatives include formamide, N-methylformamide, N,N-dimethylformamide,acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide,benzamide, and 1-cyclohexylpyrrolidone. Suitable imide derivativesinclude phthalimide, succinimide, and maleimide. Suitable carbamatederivatives include N-t-butoxycarbonyl-N,N-dicyclohexylamine,N-t-butoxycarbonylbenzimidazole and oxazolidinone.

In addition, organic nitrogen-containing compounds of the followinggeneral formula (B)-1 may also be included alone or in admixture.

N(X)_(n)(Y)_(3-n)   (B)-1

In the formula, n is equal to 1, 2 or 3; side chain Y is independentlyhydrogen or a straight, branched or cyclic C₁-C₂₀ alkyl group which maycontain an ether or hydroxyl group; and side chain X is independentlyselected from groups of the following general formulas (X1) to (X3), andtwo or three X's may bond together to form a ring.

In the formulas, R³⁰⁰, R³⁰² and R³⁰⁵ are independently straight orbranched C₁-C₄ alkylene groups; R³⁰¹ and R³⁰⁴ are independently hydrogenor a straight, branched or cyclic C₁-C₂₀ alkyl group which may containat least one hydroxyl, ether, ester group or lactone ring; R³⁰³ is asingle bond or a straight or branched C₁-C₄ alkylene group; and R³⁰⁶ isa straight, branched or cyclic C₁-C₂₀ alkyl group which may contain atleast one hydroxyl, ether, ester group or lactone ring.

Illustrative examples of the compounds of formula (B)-1 includetris(2-methoxymethoxyethyl)amine, tris{2-(2-methoxyethoxy)ethyl}amine,tris{2-(2-methoxyethoxymethoxy)ethyl}amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris{2-(1-ethoxypropoxy)ethyl}amine,tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine,4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane,4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane,1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane, 1-aza-12-crown-4,1-aza-15crown-5, 1-aza-18-crown-6, tris(2-formyloxyethyl)amine,tris(2-acetoxyethyl)amine, tris(2-propionyloxyethyl)amine,tris(2-butyryloxyethyl)amine, tris(2-isobutyryloxyethyl)amine,tris(2-valeryloxyethyl)amine, tris(2-pivaloyloxyethyl)amine,N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylamine,tris(2-methoxycarbonyloxyethyl)amine,tris(2-tert-butoxycarbonyloxyethyl)amine,tris[2-(2-oxopropoxy)ethyl]amine,tris[2-(methoxycarbonylmethyl)oxyethyl]amine,tris[2-(tert-butoxycarbonylmethyloxy)ethyl]amine,tris[2-(cyclohexyloxycarbonylmethyloxy)ethyl]amine,tris(2-methoxycarbonylethyl)amine, tris(2-ethoxycarbonylethyl)amine,N,N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine,N,N-bis(2-acetoxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)-ethylamine,N,N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)-ethylamine,N,N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxy-carbonyl]ethylamine,N,N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxy-carbonyl]ethylamine,N,N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl) -2-(4-formyloxybutoxycarbonyl)-ethylamine,N,N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)-ethylamine,N,N-bis(2-methoxyethyl)-2-(methoxycarbonyl)ethylamine,N-(2-hydroxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-hydroxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(3-hydroxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(3-acetoxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-methoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(2-methoxyethoxycarbonyl)ethyl]amine,N-methyl-bis(2-acetoxyethyl)amine, N-ethyl-bis(2-acetoxyethyl)amine,N-methyl-bis(2-pivaloyloxyethyl)amine,N-ethyl-bis[2-(methoxycarbonyloxy)ethyl]amine,N-ethyl-bis[2-(tert-butoxycarbonyloxy)ethyl]amine,tris(methoxycarbonylmethyl)amine, tris(ethoxycarbonylmethyl)amine,N-butyl-bis(methoxycarbonylmethyl)amine,N-hexyl-bis(methoxycarbonylmethyl)amine, andβ-(diethylamino)-δ-valerolactone.

Also useful are one or more organic nitrogen-containing compounds havingcyclic structure represented by the following general formula (B)-2.

Herein X is as defined above, and R³⁰⁷ is a straight or branched C₂-C₂₀alkylene group which may contain one or more carbonyl, ether, ester orsulfide groups.

Illustrative examples of the organic nitrogen-containing compoundshaving formula (B)-2 include 1-[2-(methoxymethoxy)ethyl]pyrrolidine,1-[2-(methoxymethoxy)ethyl]piperidine,4-[2-(methoxymethoxy)ethyl]morpholine,1-[2-[(2-methoxyethoxy)methoxy]ethyl]pyrrolidine,1-[2-[(2-methoxyethoxy)methoxy]ethyl]piperidine,4-[2-[(2-methoxyethoxy)methoxy]ethyl]morpholine, 2-(1-pyrrolidinyl)ethylacetate, 2-piperidinoethyl acetate, 2-morpholinoethyl acetate,2-(1-pyrrolidinyl)ethyl formate, 2-piperidinoethyl propionate,2-morpholinoethyl acetoxyacetate, 2-(1-pyrrolidinyl)ethylmethoxyacetate, 4-[2-(methoxycarbonyloxy)ethyl]morpholine,1-[2-(t-butoxycarbonyloxy)ethyl]piperidine,4-[2-(2-methoxyethoxycarbonyloxy)ethyl]morpholine, methyl3-(1-pyrrolidinyl)propionate, methyl 3-piperidinopropionate, methyl3-morpholinopropionate, methyl 3-(thiomorpholino)propionate, methyl2-methyl-3-(1-pyrrolidinyl)propionate, ethyl 3-morpholinopropionate,methoxycarbonylmethyl 3-piperidinopropionate, 2-hydroxyethyl3-(1-pyrrolidinyl)propionate, 2-acetoxyethyl 3-morpholinopropionate,2-oxotetrahydrofuran-3-yl 3-(1-pyrrolidinyl)propionate,tetrahydrofurfuryl 3-morpholinopropionate, glycidyl3-piperidinopropionate, 2-methoxyethyl 3-morpholinopropionate,2-(2-methoxyethoxy)ethyl 3-(1-pyrrolidinyl)propionate, butyl3-morpholinopropionate, cyclohexyl 3-piperidinopropionate,α-(1-pyrrolidinyl)methyl-γ-butyrolactone, β-piperidino-γ-butyrolactone,β-morpholino-δ-valerolactone, methyl 1-pyrrolidinylacetate, methylpiperidinoacetate, methyl morpholinoacetate, methylthiomorpholinoacetate, ethyl 1-pyrrolidinylacetate, 2-methoxyethylmorpholinoacetate, 2-morpholinoethyl 2-methoxyacetate, 2-morpholinoethyl2-(2-methoxyethoxy)acetate, 2-morpholinoethyl2-[2-(2-methoxyethoxy)ethoxy]acetate, 2-morpholinoethyl hexanoate,2-morpholinoethyl octanoate, 2-morpholinoethyl decanoate,2-morpholinoethyl laurate, 2-morpholinoethyl myristate,2-morpholinoethyl palmitate, and 2-morpholinoethyl stearate.

Also, one or more organic nitrogen-containing compounds having cyanogroup represented by the following general formulae (B)-3 to (B)-6 maybe blended.

Herein, X, R³⁰⁷ and n are as defined above, and R³⁰⁸ and R³⁰⁹ are eachindependently a straight or branched C₁-C₄ alkylene group.

Illustrative examples of the organic nitrogen-containing compoundshaving cyano represented by formulae (B)-3 to (B)-6 include3-(diethylamino)propiononitrile,N,N-bis(2-hydroxyethyl)-3-aminopropiononitrile,N,N-bis(2-acetoxyethyl)-3-aminopropiononitrile,N,N-bis(2-formyloxyethyl)-3-aminopropiononitrile,N,N-bis(2-methoxyethyl)-3-aminopropiononitrile,N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile, methylN-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropionate, methylN-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropionate, methylN-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropionate,N-(2-cyanoethyl)-N-ethyl-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropiononitrile,N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-formyloxyethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(3-hydroxy-1-propyl)-3-aminopropiononitrile,N-(3-acetoxy-1-propyl) -N-(2-cyanoethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(3-formyloxy-1-propyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-tetrahydrofurfuryl-3-aminopropiononitrile,N,N-bis(2-cyanoethyl)-3-aminopropiononitrile, diethylaminoacetonitrile,N,N-bis(2-hydroxyethyl)aminoacetonitrile,N,N-bis(2-acetoxyethyl)aminoacetonitrile,N,N-bis(2-formyloxyethyl)aminoacetonitrile,N,N-bis(2-methoxyethyl)aminoacetonitrile,N,N-bis[2-(methoxymethoxy)ethyl]aminoacetonitrile, methylN-cyanomethyl-N-(2-methoxyethyl)-3-aminopropionate, methylN-cyanomethyl-N-(2-hydroxyethyl)-3-aminopropionate, is methylN-(2-acetoxyethyl)-N-cyanomethyl-3-aminopropionate,N-cyanomethyl-N-(2-hydroxyethyl)aminoacetonitrile,N-(2-acetoxyethyl)-N-(cyanomethyl)aminoacetonitrile,N-cyanomethyl-N-(2-formyloxyethyl)aminoacetonitrile,N-cyanomethyl-N-(2-methoxyethyl)aminoacetonitrile,N-cyanomethyl-N-[2-(methoxymethoxy)ethyl)aminoacetonitrile,N-cyanomethyl-N-(3-hydroxy-1-propyl)aminoacetonitrile,N-(3-acetoxy-1-propyl)-N-(cyanomethyl)aminoacetonitrile,N-cyanomethyl-N-(3-formyloxy-1-propyl)aminoacetonitrile,N,N-bis(cyanomethyl)aminoacetonitrile, 1-pyrrolidinepropiononitrile,1-piperidinepropiononitrile, 4-morpholinepropiononitrile,1-pyrrolidineacetonitrile, 1-piperidineacetonitrile,4-morpholineacetonitrile, cyanomethyl 3-diethylaminopropionate,cyanomethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-acetoxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-formyloxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-methoxyethyl)-3-aminopropionate, cyanomethylN,N-bis[2-(methoxymethoxy)ethyl]-3-amino-propionate, 2-cyanoethyl3-diethylaminopropionate, 2-cyanoethylN,N-bis(2-hydroxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-acetoxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-formyloxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-methoxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis[2-(methoxymethoxy)ethyl]-3-amino-propionate, cyanomethyl1-pyrrolidinepropionate, cyanomethyl 1-piperidinepropionate, cyanomethyl4-morpholinepropionate, 2-cyanoethyl 1-pyrrolidinepropionate,2-cyanoethyl 1-piperidinepropionate, and 2-cyanoethyl4-morpholinepropionate.

Also included are organic nitrogen-containing compounds having animidazole structure and a polar functional group, represented by thegeneral formula (B)-7.

Herein, R³¹⁰ is a straight, branched or cyclic alkyl group of 2 to 20carbon atoms bearing at least one polar functional group selected fromamong hydroxyl, carbonyl, ester, ether, sulfide, carbonate, cyano andacetal groups; R³¹¹, R³¹² and R³¹³ are each independently a hydrogenatom, a straight, branched or cyclic alkyl group, aryl group or aralkylgroup having 1 to 10 carbon atoms.

Also included are organic nitrogen-containing compounds having abenzimidazole structure and a polar functional group, represented by thegeneral formula (B)-8.

Herein, R³¹⁴ is a hydrogen atom, a straight, branched or cyclic alkylgroup, aryl group or aralkyl group having 1 to 10 carbon atoms. R³¹⁵ isa polar functional group-bearing, straight, branched or cyclic C₁-C₂₀alkyl group, and the alkyl group contains as the polar functional groupat least one group selected from among ester, acetal and cyano groups,and may additionally contain at least one group selected from amonghydroxyl, carbonyl, ether, sulfide and carbonate groups.

Further included are heterocyclic nitrogen-containing compounds having apolar functional group, represented by the general formulae (B)-9 and(B)-10.

Herein, A is a nitrogen atom or ≡C—R³²², B is a nitrogen atom or≡C—R³²³, R³¹⁶ is a straight, branched or cyclic alkyl group of 2 to 20carbon atoms bearing at least one polar functional group selected fromamong hydroxyl, carbonyl, ester, ether, sulfide, carbonate, cyano andacetal groups, R³¹⁷, R³¹⁸, R³¹⁹ and R³²⁰ are each independently ahydrogen atom, a straight, branched or cyclic alkyl group or aryl grouphaving 1 to 10 carbon atoms, or a pair of R³¹⁷ and R³¹⁸ and a pair ofR³¹⁹ and R³²⁰ may bond together to form a benzene, naphthalene orpyridine ring with the carbon atoms to which they are attached; R³²¹ isa hydrogen atom, a straight, branched or cyclic alkyl group or arylgroup having 1 to 10 carbon atoms; R³²² and R³²³ each are a hydrogenatom, a straight, branched or cyclic alkyl group or aryl group having 1to 10 carbon atoms, or a pair of R³²¹ and R³²³ may bond together to forma benzene or naphthalene ring with the carbon atoms to which they areattached.

Also included are organic nitrogen-containing compounds of aromaticcarboxylic ester structure having the general formulae (B)-11 to (B)-14.

Herein R³²⁴ is a C₆-C₂₀ aryl group or C₄-C₂₀ hetero-aromatic group, inwhich some or all of hydrogen atoms may be replaced by halogen atoms,straight, branched or cyclic C₁-C₂₀ alkyl groups, C₆-C₂₀ aryl groups,C₇-C₂₀ aralkyl groups, C₁-C₁₀ alkoxy groups, C₁-C₁₀ acyloxy groups orC₁-C₁₀ alkylthio groups. R³²⁵ is CO₂R³²⁶, OR³²⁷ or cyano group. R³²⁶ isa C₁-C₁₀ alkyl group, in which some methylene groups may be replaced byoxygen atoms. R³²⁷ is a C₁-C₁₀ alkyl or acyl group, in which somemethylene groups may be replaced by oxygen atoms. R³²⁸ is a single bond,methylene, ethylene, sulfur atom or —O(CH₂CH₂O)_(n)— group wherein n is0, 1, 2, 3 or 4. R³²⁹ is hydrogen, methyl, ethyl or phenyl. X is anitrogen atom or CR³³⁰. Y is a nitrogen atom or CR³³¹. Z is a nitrogenatom or CR³³². R³³⁰, R³³¹ and R³³² are each independently hydrogen,methyl or phenyl. Alternatively, a pair of R³³⁰ and R³³¹ or a pair ofR³³¹ and R³³² may bond together to form a C₆-C₂₀ aromatic ring or C₂-C₂₀hetero-aromatic ring with the carbon atoms to which they are attached.

Further included are organic nitrogen-containing compounds of7-oxanorbornane-2-carboxylic ester structure having the general formula(B)-15.

Herein R³³³ is hydrogen or a straight, branched or cyclic C₁-C₁₀ alkylgroup. R³³⁴ and R³³⁵ are each independently a C₁-C₂₀ alkyl group, C₆-C₂₀aryl group or C₇-C₂₀ aralkyl group, which may contain one or more polarfunctional groups selected from among ether, carbonyl, ester, alcohol,sulfide, nitrile, amine, imine, and amide and in which some hydrogenatoms may be replaced by halogen atoms. R 334 and R³³⁵ may bond togetherto form a heterocyclic or hetero-aromatic ring of 2 to 20 carbon atomswith the nitrogen atom to which they are attached.

The organic nitrogen-containing compounds may be used alone or inadmixture of two or more. The organic nitrogen-containing compound ispreferably formulated in an amount of 0.001 to 2 parts, and especially0.01 to 1 part by weight, per 100 parts by weight of the base resin. Atleast 0.001 phr of the nitrogen-containing compound achieves a desiredaddition effect whereas up to 2 phr minimizes a risk of loweringsensitivity.

If desired, the resist composition of the invention may include asurfactant which is commonly used for improving the coatingcharacteristics. It may be added in conventional amounts so long as thisdoes not compromise the objects of the invention.

Nonionic surfactants are preferred, examples of which includeperfluoroalkylpolyoxyethylene ethanols, fluorinated alkyl esters,perfluoroalkylamine oxides, perfluoroalkyl EO-addition products, andfluorinated organosiloxane compounds. Useful surfactants arecommercially available under the trade names Fluorad FC-430 and FC-431from Sumitomo 3M, Ltd., Surflon S-141, S-145, KH-10, KH-20, KH-30 andKH-40 from Asahi Glass Co., Ltd., Unidyne DS-401, DS-403 and DS-451 fromDaikin Industry Co., Ltd., Megaface F-8151 from Dai-Nippon Ink &Chemicals, Inc., and X-70-092 and X-70-093 from Shin-Etsu Chemical Co.,Ltd. Preferred surfactants are is Fluorad FC-430 from Sumitomo 3M, Ltd.,KH-20 and KH-30 from Asahi Glass Co., Ltd., and X-70-093 from Shin-EtsuChemical Co., Ltd.

Also, if desired, other components including dissolution regulators,carboxylic acid compounds and acetylene alcohol derivatives may be addedto the resist composition of the invention. Optional components may beadded in conventional amounts so long as this does not compromise theobjects of the invention.

Dissolution Regulator

The dissolution regulator which can be added to the resist compositionis a compound having on the molecule at least two phenolic hydroxylgroups, in which an average of from 0 to 100 mol % of all the hydrogenatoms on the phenolic hydroxyl groups are replaced by acid labile groupsor a compound having on the molecule at least one carboxyl group, inwhich an average of 50 to 100 mol % of all the hydrogen atoms on thecarboxyl groups are replaced by acid labile groups, both the compoundshaving a weight average molecular weight within a range of 100 to 1,000,and preferably 150 to 800.

The degree of substitution of the hydrogen atoms on the phenolichydroxyl groups with acid labile groups is on average at least 0 mol %,and preferably at least 30 mol %, of all the phenolic hydroxyl groups.The upper limit is 100 mol %, and preferably 80 mol %. The degree ofsubstitution of the hydrogen atoms on the carboxyl groups with acidlabile groups is on average at least 50 mol %, and preferably at least70 mol %, of all the carboxyl groups, with the upper limit being 100 mol%.

Preferable examples of such compounds having two or more phenolichydroxyl groups or compounds having at least one carboxyl group includethose of formulas (D1) to (D14) below.

In these formulas, R²⁰¹ and R²⁰² are each hydrogen or a straight orbranched C₁-C₈ alkyl or alkenyl group, for example, hydrogen, methyl,ethyl, butyl, propyl, ethynyl and cyclohexyl.

R²⁰³ is hydrogen, a straight or branched C₁-C₈ alkyl or alkenyl group,or —(R²⁰⁷)_(h)—COOH wherein R²⁰⁷ is a straight or branched C₁-C₁₀alkylene and h is 0 or 1, for example, those exemplified for R²⁰¹ andR²⁰² and —COOH and —CH₂COOH.

R²⁰⁴ is —(CH₂)_(i)— wherein i=2 to 10, C₆-C₁₀ arylene, carbonyl,sulfonyl, an oxygen atom, or a sulfur atom, for example, ethylene,phenylene, carbonyl, sulfonyl, oxygen atom or sulfur atom.

R²⁰⁵ is a C₁-C₁₀ alkylene, a C₆-C₁₀ arylene, carbonyl, sulfonyl, anoxygen atom, or a sulfur atom, for example, methylene and thoseexemplified for R²⁰⁴.

R²⁰⁶ is hydrogen, a straight or branched C₁-C₈ alkyl or alkenyl group,or a phenyl or naphthyl group having hydroxyl substituted thereon, forexample, hydrogen, methyl, ethyl, butyl, propyl, ethynyl, cyclohexyl,hydroxyl-substituted phenyl, and hydroxyl-substituted naphthyl.

R²⁰⁸ is hydrogen or hydroxyl.

The letter j is an integer from 0 to 5; u and h are each 0 or 1; s, t,s′, t′, s″, and t″ are each numbers which satisfy s+t=8, s′+t′=5, ands″+t″=4, and are such that each phenyl skeleton has at least onehydroxyl group; and a is a number such that the compounds of formula(D8) or (D9) have a weight average molecular weight of from 100 to1,000.

Exemplary acid labile groups on the dissolution regulator include avariety of such groups, typically groups of the general formulae (L1) to(L4), tertiary alkyl groups of 4 to 20 carbon atoms, trialkylsilylgroups in which each of the alkyls has 1 to 6 carbon atoms, and oxoalkylgroups of 4 to 20 carbon atoms. Examples of the respective groups are aspreviously described.

The dissolution regulator may be formulated in an amount of 0 to 50parts, preferably 0 to 40 parts, and more preferably 0 to 30 parts byweight, per 100 parts by weight of the base resin, and may be usedsingly or as a mixture of two or more thereof. Up to 50 phr of thedissolution regulator minimizes a risk of slimming the patterned filmand reducing the resolution.

The dissolution regulator can be synthesized by introducing acid labilegroups into a compound having phenolic hydroxyl or carboxyl groups inaccordance with an organic chemical formulation.

In the resist composition, a carboxylic acid compound may be blended.Exemplary, non-limiting carboxylic acid compounds include one or morecompounds selected from Groups I and II below. Including this compoundimproves the PED stability of the resist and ameliorates edge roughnesson nitride film substrates.

Group I:

Compounds in which some or all of the hydrogen atoms on the phenolichydroxyl groups of the compounds of general formulas (A1) to (A10) beloware replaced by —R⁴⁰¹—COOH (wherein R⁴⁰¹ is a straight or branchedalkylene of 1 to 10 carbon atoms), and in which the molar ratio C/(C+D)of phenolic hydroxyl groups (C) to ≡C—COOH groups (D) in the molecule isfrom 0.1 to 1.0.

In these formulas, R⁴⁰² and R⁴⁰³ are each hydrogen or a straight orbranched C₁-C₈ alkyl or alkenyl; R⁴⁰⁴ is hydrogen, a straight orbranched C₁-C₈ alkyl or alkenyl, or a —(R⁴⁰⁹)_(h)—COOR′ group (R′ beinghydrogen or —R⁴⁰⁹—COOH); R⁴⁰⁵ is —(CH₂)_(i)— (wherein i is 2 to 10), aC₆-C₁₀ arylene, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom;R⁴⁰⁶ is a C₁-C₁₀ alkylene, a C₆-C₁₀ arylene, carbonyl, sulfonyl, anoxygen atom, or a sulfur atom; R⁴⁰⁷ is hydrogen, a straight or branchedC₁-C₈ alkyl or alkenyl, or a hydroxyl-substituted phenyl or naphthyl;R⁴⁰⁸ is hydrogen or methyl; R⁴⁰⁹ is a straight or branched C₁-C₁₀alkylene; R⁴¹⁰ is hydrogen, a straight or branched C₁-C₈ alkyl oralkenyl, or a —R⁴¹¹—COOH group; R⁴¹¹ is a straight or branched C₁-C₁₀alkylene; the letter j is an integer from 0 to 3; s1, t1, s2, t2, s3,t3, s4, and t4 are each numbers which satisfy s1+t1=8, s2+t2=5, s3+t3=4,and s4+t4=6, and are such that each phenyl structure has at least onehydroxyl group; u is a number from 1 to 4, h is a number from 1 to 4; κis a number such that the compound of formula (A6) may have a weightaverage molecular weight of 1,000 to 5,000; and λ is a number such thatthe compound of formula (A7) may have a weight average molecular weightof 11000 to 10,000.

Group II:

Compounds of general formulas (A11) to (A15) below.

In these formulas, R⁴⁰², R⁴⁰³, and R⁴¹¹ are as defined above; R412 ishydrogen or hydroxyl; s5 and t5 are numbers which satisfy s5≧0, t5≧0,and s5+t5=5; and h is a number from 1 to 4.

Illustrative, non-limiting examples of the compound having a carboxylgroup include compounds of the general formulas AI-1 to AI-14 and AII-1to AII-10 below.

In the above formulas, R″ is hydrogen or a —CH₂COOH group such that the—CH₂COOH group accounts for 10 to 100 mol % of R″ in each compound, κand λ are as defined above.

The compound having a ≡C—COOH group in the molecule is added in anamount ranging from 0 to 5 parts, preferably 0.1 to 5 parts, morepreferably 0.1 to 3 parts, even more preferably 0.1 to 2 parts byweight, per 100 parts by weight of the base resin. Up to 5 phr of thecompound minimizes a risk of the resist composition reducing itsresolution.

The resist composition of the invention may additionally include anacetylene alcohol derivative. Preferred acetylene alcohol derivativesare those having the general formula (S1) or (S2) below.

In the formulas, R⁵⁰¹, R⁵⁰², R⁵⁰³, R⁵⁰⁴, and R⁵⁰⁵ are each hydrogen or astraight, branched or cyclic C₁-C₈ alkyl; and X and Y are each 0 or apositive number, satisfying 0≦X≦30, 0≦Y≦30, and 0≦X+Y≦40.

Preferable examples of the acetylene alcohol derivative include Surfynol61, Surfynol 82, Surfynol 104, Surfynol 104E, Surfynol 104H, Surfynol104A, Surfynol TG, Surfynol PC, Surfynol 440, Surfynol 465, and Surfynol485 from Air Products and Chemicals Inc., and Surfynol E1004 fromNisshin Chemical Industry K.K.

The acetylene alcohol derivative is preferably added in an amount of0.01 to 2% by weight, and more preferably 0.02 to 1% by weight, based onthe weight of the resist composition. At least 0.01 wt % is fullyeffective in improving the coating operation and shelf stability. Up to2 wt % minimizes a risk of the resist composition reducing itsresolution.

Crosslinker

To the resist composition, any of crosslinkers which are commonly usedin negative resist compositions may be added if desired. Typicalcrosslinkers are compounds having at least two hydroxymethyl,alkoxymethyl, epoxy or vinyl ether groups in a molecule. Substitutedglycoluril derivatives, urea derivatives, andhexa(methoxymethyl)melamine compounds are suitable.

Examples include N,N,N′,N′-tetramethoxymethylurea,hexamethoxymethylmelamine, tetraalkoxymethyl-substituted glycolurilcompounds such as tetrahydroxymethyl-substituted glycoluril andtetramethoxymethylglycoluril, and condensates of phenolic compounds suchas substituted or unsubstituted bis(hydroxymethylphenol) compounds andbisphenol A with epichlorohydrin. Especially preferred crosslinkersinclude 1,3,4,6-tetraalkoxymethylglycolurils such as1,3,4,6-tetramethoxymethylglycoluril, as well as1,3,4,6-tetrahydroxymethylglycoluril, 2,6-dihydroxymethyl-p-cresol,2,6-dihydroxymethylphenol, 2,2′,6,6′-tetrahydroxymethyl-bisphenol A,1,4-bis[2-(2-hydroxypropyl)]benzene, N,N,N′,N′-tetramethoxymethylurea,and hexamethoxymethylmelamine.

An appropriate amount of the crosslinker is, but not limited thereto, 1to 25 parts, and especially 5 to 20 parts by weight per 100 parts byweight of the base resin in the resist composition. The crosslinkers maybe used alone or in admixture of any.

Protective Coating

The resist composition of the invention may be used in a pattern formingprocess adopting the immersion lithography. In the preferred immersionlithography, a protective layer is formed on a photoresist layer, and aliquid is held between the protective layer and a projection lens. Thatis, the protective layer intervenes between the photoresist layer andthe liquid. The protective layer is preferably an alkali-solubleprotective layer based on a polymer having α-trifluoromethylalcoholgroups as the alkali-soluble group. The polymers havingα-trifluoromethylalcohol groups may be obtained through polymerizationof monomers similar to the monomers from which recurring units (b-1) informulae (1) and (2) are derived. Also, monomers similar to the monomersfrom which recurring units (b-2) in formulae (1) and (2) are derived maybe copolymerized for preventing water penetration and/or improving areceding contact angle. Moreover, monomers having alkali-soluble groupsin the form of α-trifluoromethylalcohol groups as shown below may bepolymerized.

Also, monomers having a water repellent group may be polymerized,examples of which are shown below.

Provided that A stands for a proportion of a monomer having aα-trifluoromethylalcohol group, B stands for a proportion of a monomersimilar to the monomers from which recurring units (b-2) are derived, Cstands for a proportion of a monomer having a water repellent group, andA+B+C=100 mol %, these monomers are preferably (co)polymerized in suchproportions that A is in the range of 10 to 100 mol %, more specifically30 to 100 mol %, B is in the range of 0 to 90 mol %, more specifically 0to 70 mol %, C is in the range of 0 to 90 mol %, more specifically 0 to70 mol %. The polymer thus obtained is preferred as a protective coatingmaterial.

The protective coating should preferably have an alkali dissolution rateof at least 50 nm/sec, and more preferably at least 100 nm/sec, asmeasured in an aqueous solution of 2.38 wt % tetramethylammoniumhydroxide. The polymer for the protective coating should preferably havea weight average molecular weight of 1,000 to 100,000.

The solvent used for protective coating is not particularly limitedalthough those solvents in which resist layers can be dissolved shouldbe avoided. It is recommended to avoid the use of conventional resistsolvents, for example, ketones such as cyclohexanone andmethyl-2-n-amylketone; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and 1-ethoxy-2-propanol; etherssuch as propylene glycol monomethyl ether, ethylene glycol monomethylether, propylene glycol monoethyl ether, ethylene glycol monoethylether, propylene glycol dimethyl ether, and diethylene glycol dimethylether; and esters such as propylene glycol monomethyl ether acetate,propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate,butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate,tert-butyl acetate, tert-butyl propionate, and propylene glycolmono-tert-butyl ether acetate.

Suitable solvents in which resist layers are not dissolvable includenonpolar solvents, for example, higher alcohols of at least 4 carbonatoms, toluene, xylene, anisole, hexane, cyclohexane and ethers. Ofthese, higher alcohols of at least 4 carbon atoms are most desirable.

Examples of suitable solvents include, but are not limited to, 1-butylalcohol, 2-butyl alcohol, isobutyl alcohol, tert-butyl alcohol,1-pentanol, 2-pentanol, 3-pentanol, tert-amyl alcohol, neopentylalcohol, 2-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl-3-pentanol,cyclopentanol, 1-hexanol, 2-hexanol, 3-hexanol, 2,3-dimethyl-2-butanol,3,3-dimethyl-1-butanol, 3,3-dimethyl-2-butanol, 2,2′-diethyl-1-butanol,2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-methyl-3-pentanol,3-methyl-1-pentanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol,4-methyl-1-pentanol, 4-methyl-2-pentanol, 4-methyl-3-pentanol, andcyclohexanol as well as diisopropyl ether, diisobutyl ether, diisopentylether, di-n-pentyl ether, methylcyclopentyl ether, and methylcyclohexylether. These solvents may be used alone or in admixture.

Fluorinated solvents are also preferred because resist layers are notdissolvable therein. Examples include, but are not limited to,2-fluoroanisole, 3-fluoroanisole, 4-fluoroanisole, 2,3-difluoroanisole,2,4-difluoroanisole, 2,5-difluoroanisole, 5,8-difluoro-1,4-benzodioxane,2,3-difluorobenzyl alcohol, 1,3-difluoro-2-propanol,2′,4′-difluoropropiophenone, 2,4-difluorotoluene, trifluoroacetaldehydeethyl hemiacetal, trifluoroacetamide, trifluoroethanol,2,2,2-trifluoroethyl butyrate, ethyl heptafluorobutyrate, ethylheptafluorobutylacetate, ethyl hexafluoroglutarylmethyl, ethyl3-hydroxy-4,4,4-trifluorobutyrate, ethyl2-methyl-4,4,4-trifluoroacetoacetate, ethyl pentafluorobenzoate, ethylpentafluoropropionate, ethyl pentafluoropropynylacetate, ethylperfluorooctanoate, ethyl 4,4,4-trifluoroacetoacetate, ethyl4,4,4-trifluorobutyrate, ethyl 4,4,4-trifluorocrotonate, ethyltrifluorosulfonate, ethyl 3-(trifluoromethyl)butyrate, ethyltrifluoropyruvate, S-ethyl trifluoroacetate, fluorocyclohexane,2,2,3,3,4,4,4-heptafluoro-1-butanol,1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedione,1,1,1,3,5,5,5-heptafluoropentane-2,4-dione,3,3,4,4,5,5,5-heptafluoro-2-pentanol,3,3,4,4,5,5,5-heptafluoro-2-pentanone, isopropyl4,4,4-trifluoroacetoacetate, methyl perfluorodecanoate, methylperfluoro(2-methyl-3-oxahexanoate), methyl perfluorononanoate, methylperfluorooctanoate, methyl 2,3,3,3-tetrafluoropropionate, methyltrifluoroacetoacetate, 1,1,1,2,2,6,6,6-octafluoro-2,4-hexanedione,2,2,3,3,4,4, 5,5-octafluoro-1-pentanol, 1H,1H,2H,2H-perfluoro-1-decanol,perfluoro(2,5-dimethyl-3,6-dioxane anionic) acid methyl ester,2H-perfluoro-5-methyl-3,6-dioxanonane,1H,1H,2H,3H,3H-perfluorononane-1,2-diol, 1H,1H,9H-perfluoro-1-nonanol,1H,1H-perfluorooctanol, 1H,1H,2H,2H-perfluorooctanol,2H-perfluoro-5,8,11,14-tetramethyl-3,6,9,12,15-pentaoxa-octadecane,perfluorotributylamine, perfluorotrihexylamine, methylperfluoro-2,5,8-trimethyl-3,6,9-trioxadodecanoate.perfluorotripentylamine, perfluorotripropylamine,1H,1H,2H,3H,3H-perfluoroundecane-1,2-diol, trifluorobutanol,1,1,1-trifluoro-5-methyl-2,4-hexanedione, 1,1,1-trifluoro-2-propanol,3,3,3-trifluoro-1-propanol, 1,1,1-trifluoro-2-propyl acetate,perfluorobutyltetrahydrofuran, perfluorodecalin,perfluoro(1,2-dimethylcyclohexane), perfluoro(1,3-dimethylcyclohexane),propylene glycol trifluoromethyl ether acetate, propylene glycol methylether trifluoromethyl acetate, butyl trifluoromethylacetate, methyl3-trifluoromethoxypropionate, perfluorocyclohexanone, propylene glycoltrifluoromethyl ether, butyl trifluoroacetate,1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione,1,1,1,3,3,3-hexafluoro-2-propanol,1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol,2,2,3,4,4,4-hexafluoro-1-butanol, 2-trifluoromethyl-2-propanol,2,2,3,3-tetrafluoro-1-propanol, 3,3,3-trifluoro-1-propanol, and4,4,4-trifluoro-1-butanol, which may be used alone or in admixture.

Process

The invention also provides a pattern forming process comprising thesteps of applying the aforementioned resist composition onto a substrateto form a coating, heat treating the coating, exposing it to high-energyradiation, and developing the exposed coating with a developer. Thepreferred high-energy radiation has a wavelength in the range of 180 to250 nm.

The exposing step may be performed by immersion lithography involvingexposing the coating to high-energy radiation through a liquid. In anexemplary embodiment of the immersion lithography, high-energy radiationhaving a wavelength of 180 to 250 nm is used, a liquid is introducedbetween the substrate having a resist coating and an optional protectivecoating formed thereon and a projection lens, and the substrate isexposed to the high-energy radiation through the liquid. An exemplaryliquid is water.

In forming a resist pattern from the resist composition of theinvention, any well-known lithography may be used. For example, theresist composition is applied onto a substrate (e.g., Si, SiO₂, SiN,SiON, TiN, WSi, BPSG, SOG, low-dielectric-constant film, etc.) forintegrated circuit microfabrication by a suitable coating technique suchas spin coating. The coating is prebaked on a hot plate at 50 to 150° C.for about 1 to 10 minutes, preferably at 60 to 140° C. for 1 to 5minutes. The resulting resist film is generally 10 to 200 nm thick.

By forming an antireflective coating (ARC) between the substrate forintegrated circuit microfabrication and the photoresist, substratereflection may be suppressed. Suitable antireflective coatings includeinorganic coatings of amorphous carbon and SiON and organic coatingsformed by spin coating, with the latter being widely employed.

As the immersion lithography uses a projection lens having a NA inexcess of 1 and allows the incident angle of light to the resist and ARCto increase, the prior-art single-layer ARC is difficult to controlreflection. In this regard, bilayer ARC has been proposed. Also toovercome a lowering of etching margin by a thickness reduction of resistfilm, a trilayer process has been proposed involving forming asilicon-containing film as an underlay beneath the resist, and formingan undercoat layer with a high carbon density on a substrate forintegrated circuit microfabrication. Films each consisting of one ormore of many various layers may be formed beneath the photoresist.

After a photoresist layer is formed on a wafer, a water-insoluble,alkali-soluble resist protective coating material is applied to thephotoresist layer by suitable techniques, typically spin coating. Thecoating thickness is preferably in a range of 10 to 500 nm. Thelithography used herein may be either dry lithography wherein a gas suchas air or nitrogen is present between the resist protective coating andthe projection lens, or immersion lithography wherein a liquid fills inbetween the resist protective coating and the projection lens. Theimmersion lithography favors water. In the immersion lithography,whether or not the wafer edge and rear side are cleaned and the cleaningtechnique are important in preventing flowing of water to the wafer rearside and leaching from the substrate. After spin coating, the resistprotective coating is baked at a temperature of 40 to 130° C. for 10 to300 seconds for evaporating off the solvent. In the case of resist layerformation and dry lithography, edge cleaning is performed during thespin coating. In the case of immersion lithography, contact of waterwith the substrate surface which is fully hydrophilic is undesirablebecause water may be left on the substrate surface at the edge. It isthen recommended to omit edge cleaning during the spin coating of theresist protective coating.

Once the resist protective coating is formed, exposure is carried out byimmersion lithography. This is followed by post-exposure bake (PEB) anddevelopment in an alkaline developer for 10 to 300 seconds. An aqueoussolution of 2.38 wt % tetramethylammonium hydroxide (TMAH), which iscommonly used as the alkaline developer, is used herein. Sometimes wateris left on the resist protective coating prior to PEB. If PEB isperformed in the presence of residual water, water can penetrate throughthe protective coating to suck up the acid in the resist, impedingpattern formation. To fully remove the water on the protective coatingprior to PEB, the water on the protective coating should be dried orrecovered by suitable means, for example, spin drying prior to PEB,purging of the protective coating surface with dry air or nitrogen, orpost-soaking after the exposure.

As discussed earlier, the photoresist layer formed from the resistcomposition of the invention substantially prevents formation of a mixedlayer with the protective coating and remains fully hydrophilic afterdevelopment, eliminating the occurrence of defects like residues knownas blobs.

Resist materials for use with mask blanks often include novolac resinsand hydroxystyrene based resins. Those resins in which hydroxyl groupsare substituted by acid labile groups are used for positive resistswhile these resins in combination with crosslinking agents are used fornegative resists. Base polymers which can be used herein includecopolymers of hydroxystyrene with one or more of (meth)acrylicderivatives, styrenes, vinyl naphthalenes, vinyl anthracenes, vinylpyrenes, hydroxyvinyl naphthalenes, hydroxyvinyl anthracenes, indenes,hydroxyindenes, acenaphthylenes, and norbornadienes.

Where the resist coating is for use with mask blanks, the photoresistcomposition of the invention is coated on a mask blank substrate ofSiO₂, Cr, CrO, CrN, MoSi or the like. By further forming a SOG film andan organic undercoat film between the photoresist and the blanksubstrate, there is provided a three-layer structure which is alsoacceptable herein. Once the resist coating is formed, the structure isexposed using an electron beam writing system. The exposure is followedby post-exposure baking (PEB) and development in an alkaline developerfor 10 to 300 seconds.

EXAMPLE

Examples of the invention are given below by way of illustration and notby way of limitation. The abbreviations used herein are GPC for gelpermeation chromatography, NMR for nuclear magnetic resonance, Mw forweight average molecular weight, Mn for number average molecular weight,and Mw/Mn for molecular weight dispersity. Mw and Mn are determined byGPC versus polystyrene standards. All parts are by weight (pbw).

Preparation of Polymers

Additive polymers to be added to resist compositions were prepared bycombining monomers, effecting copolymerization reaction in isopropylalcohol as a solvent, pouring the polymerization solution into hexanefor crystallization, washing the polymer with hexane, repeating thecrystallization and washing steps, isolating and drying. The resultingpolymers were analyzed for composition by ¹H-NMR and for Mw and Mw/Mn byGPC.

Preparation of Resist Compositions

Resist compositions, designated Resists 1 to 5, were prepared bycombining and dissolving a base resin, a photoacid generator, and abasic compound in an organic solvent in accordance with the recipe shownbelow, and filtering through a Teflon® filter having a pore size of 0.2μm. It is noted that Resists 1 to 4 are positive and Resist 5 having acrosslinker added thereto is negative.

Resist 1

Mixing composition:

Base Resin 1 100 pbw PAG-1  5 pbw Basic compound  1 pbw Organic solvent1 1330 pbw  Organic solvent 2 570 pbw

Base Resin 1 has the following structural formula.

-   PAG-1: triphenylsulfonium nonafluorobutane-sulfonate-   Basic compound (Quencher 1): 2-cyclohexylcarboxyethylmorpholine-   Organic solvent 1: 1-methoxyisopropyl acetate-   Organic solvent 2: cyclohexanone

Resist 2

Mixing composition:

Base Resin 2 100 pbw PAG-1  5 pbw Basic compound  1 pbw Organic solvent1 1330 pbw  Organic solvent 2 570 pbw

Base Resin 2 has the following structural formula.

-   PAG-1: triphenylsulfonium nonafluorobutane-sulfonate-   Basic compound (Quencher 1): 2-cyclohexylcarboxyethylmorpholine-   Organic solvent 1: 1-methoxyisopropyl acetate-   Organic solvent 2: cyclohexanone

Resist 3

Mixing composition:

Base Resin 1 50 pbw Base Resin 3 50 pbw PAG-1  5 pbw Basic compound  1pbw Organic solvent 1 1330 pbw  Organic solvent 2 570 pbw 

Base Resin 3 has the following structural formula.

-   PAG-1: triphenylsulfonium nonafluorobutane-sulfonate-   Basic compound (Quencher 1): 2-cyclohexylcarboxyethylmorpholine-   Organic solvent 1: 1-methoxyisopropyl acetate-   Organic solvent 2: cyclohexanone

Resist 4

Mixing composition:

Base Resin 2 50 pbw Base Resin 4 50 pbw PAG-1 5 pbw Basic compound 1 pbwOrganic solvent 1 1330 pbw Organic solvent 2 570 pbw

Base Resin 4 has the following structural formula.

-   PAG-1: triphenylsulfonium nonafluorobutane-sulfonate-   Basic compound (Quencher 1): 2-cyclohexylcarboxyethylmorpholine-   Organic solvent 1: 1-methoxyisopropyl acetate-   Organic solvent 2: cyclohexanone

Resist 5

Mixing composition:

Base Resin 5 100 pbw  PAG-1  5 pbw Basic compound  1 pbw Crosslinker 10pbw Organic solvent 1 1330 pbw  Organic solvent 2 570 pbw 

Base Resin 5 has the following structural formula.

-   PAG-1: triphenylsulfonium nonafluorobutane-sulfonate-   Basic compound (Quencher 1): 2-cyclohexylcarboxyethylmorpholine-   Crosslinker: 1,3,4,6-tetramethoxymethylglycoluril-   Organic solvent 1: 1-methoxyisopropyl acetate-   Organic solvent 2: cyclohexanone

Preparation of Protective Coating Material

Protective topcoat compositions, designated TC1 to TC3, were prepared bycombining and dissolving a base resin (TC Polymer 1, 2 or 3) in anorganic solvent in accordance with the recipe shown below, and filteringthrough a Teflon® filter having a pore size of 0.2 μm.

TC1 TC Polymer 1 100 pbw Organic solvent 3 2600 pbw  Organic solvent 4260 pbw TC2 TC Polymer 2 100 pbw Organic solvent 3 2600 pbw  Organicsolvent 4 260 pbw TC3 TC Polymer 3 100 pbw Organic solvent 3 2600 pbw Organic solvent 4 260 pbw

TC Polymers 1 to 3 have the structural formula below.

Organic solvent 3: isoamyl ether

Organic solvent 4: 2-methyl-1-butanol

Examples 1 to 35 and Comparative Examples 1 to 9

Resist coating solutions #1 to #27 were prepared by compounding theresist compositions (Resists 1 to 5) as a matrix with the above-preparedpolymers (Polymers 1 to 19) in a suitable proportion. Table 1 shows acombination and proportion of the additive polymer and the matrix resistcomposition. It is noted that the proportion of the additive polymer isexpressed in parts by weight per 100 parts by weight of the base resinin the matrix resist composition.

Each resist solution was applied onto an antireflective coating ARC-29A(Nissan Chemical Co., Ltd.) of 87 nm thick formed on a silicon substrateand baked at 110° C. for 60 seconds, forming a resist film of 150 nmthick. In Examples 28 to 35, a protective topcoat solution was coatedthereon and baked at 100° C. for 60 seconds, forming a protectivecoating of 50 nm thick (TC1, TC2 or TC3). The structure was exposed bymeans of an ArF scanner model S307E (Nikon Corp., NA 0.85, σ 0.93, 4/5annular illumination, 6% halftone phase shift mask), post-exposure baked(PEB) at 110° C. for 60 seconds, and developed with a 2.38 wt % TMAHaqueous solution for 60 seconds, forming a 75-nm line-and-space patternover the wafer surface. Mask fidelity was examined by determining a maskerror factor (MEF) of the 75-nm line-and-space pattern. MEF is given asmeasured linewidth variation/mask linewidth variation, with smallervalues of MEF being better. A cross section of the wafer was thenobserved for comparing the pattern profile.

In Comparative Examples 1 to 9, the additive polymers (Polymers 1 to 19)were not added. In Comparative Examples 6 to 9, the protective coatingwas applied.

TABLE 1 Matrix Protective Pattern resist topcoat Additive polymerprofile after Resist solution composition material (amount) developmentMEF Example 1 Resist solution #1 Resist 1 — Polymer 1 (3 pbw)Rectangular 3.1 2 Resist solution #2 Resist 1 — Polymer 2 (3 pbw)Rectangular 3.3 3 Resist solution #3 Resist 1 — Polymer 3 (3 pbw)Rectangular 3.4 4 Resist solution #4 Resist 1 — Polymer 4 (3 pbw)Rectangular 3.1 5 Resist solution #5 Resist 1 — Polymer 5 (3 pbw)Rectangular 3.5 6 Resist solution #6 Resist 1 — Polymer 6 (3 pbw)Rectangular 3.6 7 Resist solution #7 Resist 1 — Polymer 7 (3 pbw)Rectangular 3.5 8 Resist solution #8 Resist 1 — Polymer 8 (3 pbw)Rectangular 3.2 9 Resist solution #9 Resist 1 — Polymer 9 (3 pbw)Rectangular 3.4 10 Resist solution #10 Resist 1 — Polymer 10 (3 pbw)Rectangular 3.4 11 Resist solution #11 Resist 1 — Polymer 11 (3 pbw)Rectangular 3.7 12 Resist solution #12 Resist 1 — Polymer 12 (3 pbw)Rectangular 3.9 13 Resist solution #13 Resist 1 — Polymer 13 (3 pbw)Rectangular 3.5 14 Resist solution #14 Resist 1 — Polymer 14 (3 pbw)Rectangular 3.6 15 Resist solution #15 Resist 1 — Polymer 15 (3 pbw)Rectangular 3.2 16 Resist solution #16 Resist 1 — Polymer 16 (3 pbw)Rectangular 3.7 17 Resist solution #17 Resist 1 — Polymer 17 (3 pbw)Rectangular 3.6 18 Resist solution #18 Resist 1 — Polymer 18 (3 pbw)Rectangular 3.3 19 Resist solution #19 Resist 1 — Polymer 19 (3 pbw)Rectangular 3.3 20 Resist solution #20 Resist 2 — Polymer 2 (3 pbw)Rectangular 3.2 21 Resist solution #21 Resist 2 — Polymer 15 (3 pbw)Rectangular 3.1 22 Resist solution #22 Resist 3 — Polymer 2 (3 pbw)Rectangular 3.4 23 Resist solution #23 Resist 3 — Polymer 15 (3 pbw)Rectangular 3.4 24 Resist solution #24 Resist 4 — Polymer 2 (3 pbw)Rectangular 3.3 25 Resist solution #25 Resist 4 — Polymer 15 (3 pbw)Rectangular 3.7 26 Resist solution #26 Resist 5 — Polymer 2 (3 pbw)Rectangular 3.9 27 Resist solution #27 Resist 5 — Polymer 15 (3 pbw)Rectangular 3.6 28 Resist solution #1 Resist 1 TC1 Polymer 1 (3 pbw)Rectangular 3.8 29 Resist solution #7 Resist 1 TC1 Polymer 7 (3 pbw)Rectangular 3.2 30 Resist solution #12 Resist 1 TC1 Polymer 12 (3 pbw)Rectangular 3.2 31 Resist solution #15 Resist 1 TC1 Polymer 15 (3 pbw)Rectangular 3.3 32 Resist solution #20 Resist 2 TC1 Polymer 2 (3 pbw)Rectangular 3.8 33 Resist solution #1 Resist 1 TC2 Polymer 1 (3 pbw)Rectangular 3.5 34 Resist solution #15 Resist 1 TC2 Polymer 15 (3 pbw)Rectangular 3.2 35 Resist solution #1 Resist 1 TC3 Polymer 1 (3 pbw)Rectangular 3.1 Comparative 1 — Resist 1 — — Somewhat rounded top 4.8Example 2 — Resist 2 — — Rounded top 4.4 3 — Resist 3 — — Somewhatrounded top 4.8 4 — Resist 4 — — Rounded top 4.8 5 — Resist 5 — — Bulgedtop 6.5 6 — Resist 1 TC1 — Rounded top 5.2 7 — Resist 3 TC1 — Heavilyrounded top 5.3 8 — Resist 1 TC2 — Heavily rounded top 5.2 9 — Resist 1TC3 — Rounded top 5.4

As is evident from Table 1, the resist compositions having the additivepolymers compounded therein are improved in both rectangularity and MEF.Even when protective coatings are applied, these resist layers maintaina rectangularity and a MEF without degradation, and intermixing thereofwith the protective coating is inhibited.

Examples 36 to 41 and Comparative Examples 10 to 11

Resist solutions #2, #11, #13, #15, #22 and #23 were selected fromTable 1. For each, a resist film was formed on a silicon substrate as inExamples 1 to 35. A contact angle with water of the photoresist film wasmeasured, using a contact angle meter Drop Master 500 by Kyowa InterfaceScience Co., Ltd. Specifically, 5 μL of deionized water was dispensed onthe photoresist film after development. The results are shown in Table 2(Examples 36 to 41). As comparative examples, the same test was carriedout without adding the polymer of the invention. The results are alsoshown in Table 2 (Comparative Examples 10 and 11).

In a further run, resist solutions #2, #11, #13, #15, #22 and #23 wereprecision filtered through a high-density polyethylene filter with apore size of 0.02 μm. Protective topcoat composition TC1 was similarlyprecision filtered. The resist solution was applied onto anantireflective coating ARC-29A (Nissan Chemical Co., Ltd.) of 87 nmthick formed on a 8-inch silicon substrate and baked at 110° C. for 60seconds, forming a resist film of 150 nm thick. The protective topcoatsolution TC1 was coated thereon and baked at 100° C. for 60 seconds.Using an ArF scanner model S307E (Nikon Corp., NA 0.85, a 0.93, Crmask), the entire surface of the wafer was subjected to checkered-flagexposure including alternate exposure of open-frame exposed andunexposed portions having an area of 20 mm square. This was followed bypost-exposure baking (PEB) at 110° C. for 60 seconds and developmentwith a 2.38 wt % TMAH aqueous solution for 30 seconds.

Using a flaw detector Win-Win 50-1200 (Tokyo Seimitsu Co., Ltd.), thenumber of defects in the unexposed portion of the checkered-flag wascounted at the pixel size of 0.125 μm. The results are shown in Table 2.As comparative examples, the same test was carried out without addingthe polymer of the invention. The results are also shown in Table 2(Comparative Examples 10 and 11).

TABLE 2 Contact angle after Number development of Resist solution (°)defects Example 36 Resist solution #2 58 12 Example 37 Resist solution#11 55 7 Example 38 Resist solution #13 53 3 Example 39 Resist solution#15 56 10 Example 40 Resist solution #22 61 29 Example 41 Resistsolution #23 59 22 Comparative Example 10 Resist 1 65 1,020 ComparativeExample 11 Resist 3 68 2,300

As is evident from Table 2, the resist composition having the additivepolymer incorporated therein is successful in dramatically reducing thenumber of defects after development.

While the invention has been described with reference to a preferredembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

For example, although the resist composition applied to the immersionlithography has been described, it is also applicable to conventionallithography.

Japanese Patent Application No. 2007-176011 is incorporated herein byreference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

1. A resist composition comprising a polymer which changes its alkalisolubility under the action of an acid as a base resin, and a copolymercomprising recurring units containing an amino group and recurring unitscontaining at least one fluorine atom as an additive.
 2. The resistcomposition of claim 1, wherein said copolymer has the general formula(1):

wherein R¹, R⁴, and R⁷ are each independently hydrogen or methyl, X₁ andY₂ are each independently selected from the group consisting of a singlebond, —O—R⁹—, —C(═O)—O—R⁹—, —C(═O)—NH—R⁹—, a straight or branched C₁-C₄alkylene, and phenylene group, wherein R⁹ is a straight, branched orcyclic C₁-C₁₀ alkylene group which may contain an ester or ether group,n is 1 or 2, in case of n=1, Y₁ is selected from the group consisting ofa single bond, —O—R⁹—, —C(═O)—O—R⁹—, —C(═O)—NH—R⁹—, a straight orbranched C₁-C₄ alkylene, and phenylene group, wherein R⁹ is as definedabove, in case of n=2, Y₁ is selected from the group consisting of—O—R¹⁰¹═, —C(═O)—O—R¹⁰¹═, —C(═O)—NH—R¹⁰¹═, a straight or branched C₁-C₄alkylene group with one hydrogen atom eliminated, and a phenylene groupwith one hydrogen atom eliminated, wherein R¹⁰¹ is a straight, branchedor cyclic C₁-C₁₀ alkylene group with one hydrogen atom eliminated whichmay contain an ester or ether group, R² and R³ are each independentlyselected from the group consisting of hydrogen, a straight, branched orcyclic C₁-C₂₀ alkyl group, a C₂-C₂₀ alkenyl group, and a C₆-C₁₀ arylgroup, R² and R³ may bond together to form a ring of 3 to 20 carbonatoms with the nitrogen atom to which they are attached, the alkylgroup, alkenyl group, aryl group or the ring may contain a hydroxy,ether, ester, cyano, amino group, double bond or halogen atom, or R² andX₁ may bond together to form a ring of 3 to 20 carbon atoms with thenitrogen atom to which they are attached, R⁵ is a straight, branched orcyclic C₁-C₁₂ alkylene group, R⁶ is hydrogen, fluorine, methyl,trifluoromethyl or difluoromethyl, or R⁵ and R⁶ may bond together toform an aliphatic ring of 2 to 12 carbon atoms with the carbon atom towhich they are attached, which ring may contain an ether group,fluorinated alkylene group or trifluoromethyl group, R⁸ is a straight,branched or cyclic C₁-C₂₀ alkyl group which has at least one fluorineatom substituted thereon and which may contain an ether, ester orsulfonamide group, the subscripts are numbers in the range: 0<a<1.0,0≦(b-1)<1.0, 0≦(b-2)<1.0, 0<(b-1)+(b-2)<1.0, and 0.5≦a+(b-1)+(b-2) ≦1.0.3. The resist composition of claim 1, wherein said copolymer has thegeneral formula (2):

wherein R¹, R ⁴, R⁷, and R¹⁰ are each independently hydrogen or methyl,X₁ and Y₂ are each independently selected from the group consisting of asingle bond, —O—R⁹—, —C(═O)—O—R⁹—, —C(═O)—NH—R⁹—, a straight or branchedC₁-C₄ alkylene, and phenylene group, wherein R⁹ is a straight, branchedor cyclic C₁-C₁₀ alkylene group which may contain an ester or ethergroup, n and m are each independently 1 or 2, in case of n=1 and m=1, Y₁and Y₃ are each independently selected from the group consisting of asingle bond, —O—R⁹—, —C(═O)—O—R⁹—, —C(═O)—NH—R⁹—, a straight or branchedC₁-C₄ alkylene, and phenylene group, wherein R⁹ is as defined above, incase of n=2 and m=2, Y₁ and Y₃ are each independently selected from thegroup consisting of —O—R¹⁰¹═, —C(═O)—O—R¹⁰¹═, —C(═O)—NH—R¹⁰¹═, astraight or branched C₁-C₄ alkylene group with one hydrogen atomeliminated, and a phenylene group with one hydrogen atom eliminated,wherein R¹⁰¹ is a straight, branched or cyclic C₁-C₁₀ alkylene groupwith one hydrogen atom eliminated which may contain an ester or ethergroup, R² and R³ are each independently selected from the groupconsisting of hydrogen, a straight, branched or cyclic C₁-C₂₀ alkylgroup, a C₂-C₂₀ alkenyl group, and a C₆-C₁₀ aryl group, R² and R³ maybond together to form a ring of 3 to 20 carbon atoms with the nitrogenatom to which they are attached, the alkyl group, alkenyl group, arylgroup or the ring may contain a hydroxy, ether, ester, cyano, aminogroup, double bond or halogen atom, or R² and X₁ may bond together toform a ring of 3 to 20 carbon atoms with the nitrogen atom to which theyare attached, R⁵ and R¹¹ are each independently a straight, branched orcyclic C₁-C₁₂ alkylene group, R⁶ and R¹² are each independentlyhydrogen, fluorine, methyl, trifluoromethyl or difluoromethyl, or R⁵ andR⁶ may bond together to form an aliphatic ring of 2 to 12 carbon atomswith the carbon atom to which they are attached, which ring may containan ether group, fluorinated alkylene group or trifluoromethyl group, andR¹¹ and R¹² may bond together to form an aliphatic ring of 2 to 12carbon atoms with the carbon atom to which they are attached, which ringmay contain an ether group, fluorinated alkylene group ortrifluoromethyl group, R⁸ is a straight, branched or cyclic C₁-C₂₀ alkylgroup which has at least one fluorine atom substituted thereon and whichmay contain an ether, ester or sulfonamide group, R¹³ is an acid labilegroup, the subscripts are numbers in the range: 0<a<1.0, 0≦(b-1)<1.0,0≦(b-2)<1.0, 0<(b-3)<1.0, and 0.5≦a+(b-1)+(b-2)+(b-3)≦1.0.
 4. The resistcomposition of claim 1 which is a chemically amplified positive resistcomposition.
 5. The resist composition of claim 4, wherein the baseresin is a polymer comprising recurring units having an acid labilegroup and recurring units having a hydroxy group and/or adhesive groupof lactone ring.
 6. The resist composition of claim 1 which is achemically amplified negative resist composition.
 7. The resistcomposition of claim 1, further comprising at least one member selectedfrom the group consisting of an organic solvent, a basic compound, adissolution regulator, a crosslinker, and a surfactant.
 8. A patternforming process comprising the steps of: applying the resist compositionof claim 1 onto a substrate to form a coating, heat treating the coatingand exposing it to high-energy radiation, and developing the exposedcoating with a developer.
 9. The process of claim 8, wherein thehigh-energy radiation has a wavelength of 180 to 250 nm.
 10. The processof claim 8, wherein the exposing step is by immersion lithographyinvolving exposing the coating to high-energy radiation through aliquid.
 11. The process of claim 10, further comprising the step offorming a protective coating so that the protective coating intervenesbetween the photoresist coating and the liquid during the immersionlithography.
 12. The process of claim 11, wherein the protective coatingis an alkali-soluble protective film based on a polymer havingalpha-trifluoromethylhydroxy groups.
 13. The process of claim 10,wherein the immersion lithography involves using high-energy radiationhaving a wavelength of 180 to 250 nm, introducing a liquid between thesubstrate having a resist coating and a protective coating formedthereon and a projection lens, and exposing the substrate to thehigh-energy radiation through the liquid.
 14. The process of claim 10,wherein the liquid is water.